So my shihtzu bishon puppy is now 8 months. He suffered from a bad attack from our neighbor's golden retriever when he was about 3 months. And ever since, he would just go CRAZY when he sees other dogs and does not even acknowledge my commands at all. And now he goes crazy even at the sight of other people. He's a wonderful puppy at home but I really want him to be under control in public. And because of his aggression toward other dogs/maybe people, I'm scared to socialize him. My mom just told me that there's going to be this dog show thing in town this weekend where everyone can bring their dogs. My mom really wants to take him just so he gets more exposure to other people/dogs. But I'm kind of worried as to what could happen. What do you guys think? Oh and I also thought about a behaviorist but after looking it up and seeing how expensive it is, there is just no way I could afford one.

No, I would not take him to the dog show. He would be overwhelmed (imagine you are terrified of snakes. Instead of taking the time to get to know one gentle small python, you were taken to a room that was full of snakes of all shapes and sizes!)
The puppy had a horrific thing happen to him at a very young age and he was understandably traumatized. You will need to start very slowly with him to help him regain his confidence.
Do you know someone who has a very quiet, well behaved dog who gets along well with other animals? If you can find someone, have them bring the dog to your house. Just have the person bring the dog in on leash and sit down. Have the dog lie down if he knows the command. Ignore your dog and have a relaxed chat with your friend for about 30 minutes. He needs time to decide for himself that this dog is not a threat. Best case scenario, your pup comes over and investigates the newcomer and decides he is not a problem. If he won't get near the dog. That's OK. Have the person and dog leave calmly. Your dog just had an encounter with a strange dog and nothing bad happened.
You can invite them back over every few days. It is unlikely that your dog will flip out, but if he does, under no circumstance tell him "its okay"--he may interpret that as you approving of fearful behavior. Continue to ignore him, but you may need to end the visit a little sooner.
For now, if you can get him introduced to one other dog that is not scary and get him comfortable around it, that is probably as much as he can handle.
If he has to meet new people, treat the situation the same way. Have them ignore him and let him make the first move. If he comes around to investigate them they can toss a small treat on the floor near him and otherwise continue to ignore him. Don't put him in a position where he feels threatened and can't escape.
This is going to be a slow process. Don't rush it. If you can manage it, a couple of sessions with a behaviorist would be a good investment.

I would like to add that you need to drain his energy before a visit by another dog. Take him on a very long walk/run. Make sure you have him on a leash for at least the first few encounters. You have to protect the other dog too, or you could have two dogs with issues, and they could also hurt each other.

I have a calm submissive dog, and so does my neighbor. The two run back and fourth along the fence with each other everyday for almost a yr now. My dog was also attacked, so I was very careful. I thought because the two dogs knew each other through the fence, that it would be just fine to have the neighbors dog start coming into my yard so they could play that way. It did not go well. I didn't have my dog leashed, and almost immediately my dog went after her buddy. The fence was a barrier. My dog didn't hurt the other dog, but I had to pin her down (which isn't mean, only a correction) until she was calm and submissive again. I kept the other dog there, until my dog surrendered, and then took the other dog back home. We tried this many times until my dog learned that the other dog wasn't a threat. Now she is better with other dogs.

Just make sure you keep a watchful eye on both dogs body language. Watch the positioning of their tails. If their tails are standing up be careful. If they are relaxed and in the middle you should be okay. If the tail goes between the legs, be watchful of that too, because that will mean they are very insecure about the other dog, and could attack.

Good luck!

Wow so much good info. Thanks guys!

I probably won't take him to show then. With my puppy, he is always barking like crazy towards other dogs/people. Whenever our neighbor's dogs are out, he would bark nonstop and sometimes even jump onto the fence. So w/o the fence, I wouldn't be surprised if he attacks the other dogs. I don't know if I'm doing the correct thing right now. But whenever he barks like crazy, I try to look at him straight in the eye and tell him to be quiet. And if he does for a few secs, then I give him a treat. But it just seems to work for that moment. He diverts his attention to the dog/person right away. Should I pin him down? Would that decrease his confidence even more? One of our neighbors have a german shepherd and he always comes right up to the fence and looks really intense. My puppy used to be OK with our other neighbor's dog, which is a small pom/shihtzu. But just this week, he started aggressively barking at him all of a sudden. But then two seconds later, that pom/shihtzu lifted his leg and peed. I don't know if that was the cause or if my puppy is starting to become aggressive towards him too. Aahh. I'm so stressed out.

And what if I have another puppy over and have both of them on leash so that they are literally not capable to touching each other? Would that be a good way to start?

First off NO, do not give him a treat just for stopping to bark. He thinks you are rewarding his barking. Treats should only be given for training or an obeyed command, and only after they have become completely submissive after bad behaviour. When he lays down and is ignoring the other dog.

You should ALWAYS have his leash on when meeting other dogs yes. Watch his body language. If he is barking or staring intently at the other dog, he needs a correction right there and then. It is not hurting his feelings, it is teaching him, just like you would teach a child not to touch a hot stove. When you see him getting tense, or focusing too much on another dog, give him a quick 'upwards' tug ( not backwards tug) with a sharp NO, or a simple one word command, and then relax the leash. If he does it again, repeat it until he submits to it. This is an exercise to teach him that you are in charge.

You can also show him that your home, your yard, fence, etc. is your space and you make the rules. Claim it by getting in front of him, giving your command along with pointing your finger and walking towards him, and saying down/stay.

It will take some time, but you can claim your front/back doors the same way. If he just continues to bark, you can give him a "bite" All that means, is the way the pack leader with dogs control their pack. It's just a firm "bite with your hand right around the side of his neck. He is little, so you will no what force to use. This isn't mean, this is the language they understand, and their mother would have done the same.

Just looking him in the eye, and telling him to be quiet is just not going to cut it. He won't get it. He needs you to be firm, in order to teach him what is not acceptable to you, the pack leader.

Only pin him when he is having extreme behaviour, like trying to attack. Keep pinning him until he submits and is in a calm state, and is actually not paying attn anymore to the other dog. You usually pin him in the same manner as you give the "bite with your hand right around the side of his neck. He is little, so you will no what force to use. This isn't mean, this is the language they understand, and their mother would have done the same.

Just looking him in the eye, and telling him to be quiet is just not going to cut it. He won't get it. He needs you to be firm, in order to teach him what is not acceptable to you, the pack leader.

Only pin him when he is having extreme behaviour, like trying to attack. Keep pinning him until he submits and is in a calm state, and is actually not paying attn anymore to the other dog. You usually pin him in the same manner as you give the ", and maybe on the back hind if he is squirming around.

Hope that helps you some! :)