My mother has two cats, Sadie and Paige. Sadie is mean, Paige is sweet. When my son sees them he will go and lay on them, pull out their fur, and smother them with his body. He thinks he is showing them love. I have tried time outs when he is mean to the cats. And Paige starts breathing funny when he is around. How do I show him kindness to the cats?

My children have always grown up with animals (we have lots).
When they would do something that was unacceptable, I'd say with a stern voice while pointing to the animal - "No, hurt kitty - ouch". While mimicking the action they were doing to hurt the animal.
Then I'd say "love kitty" be sweet to kitty" while holding their hand in mine and showing them the proper way to pet a cat.

For instance if my children pulled the cats hair, I'd do the motion of pulling hair (on my own head) and would point to the cat and say " No, hurt kitty" "no pulling hair, it will hurt kitty - ouch"
Then I'd take their hand in mine and pet the cat the proper way while saying "love kitty, be sweet to kitty, nice kitty"

I did this all the time, even when they weren't being to rough.

Anytime I'd pet the cat or the dog while my children were around (which was always) I'd put their hand in mine and pet the dog/cat/whatever with them and I'd say stuff like "sweet kitty, love dogie, easy pet, nice pet"

Stuff like that. It worked for us.

I'd suggest petting the cats with him more often rather than letting him approach the cats himself.
It may help him to understand better.

I don't have kids, but agree with what AKaeTrue said. I'm also wondering if getting a stuffed toy to practice on might help. That way you could practice petting, and not poking, etc. On the other hand, it might also just get your son to treat real animals like toys, which is not what you want.

Also, you need to make sure he doesn't run up to them, pull on their fur, and smother them. That's just asking to be scratched, at a minimum. We rely on pet owners to control their pets so that they don't hurt children. But we also need to rely on parents to control their children so that they don't hurt pets.