Does ethical relativism justify the view that it is OBJECTIVELY morally right to be tolerant of the different ethical behavior of people in other cultures?

Ethical relativism, among other things, questions the idea that any ethical perspective is privileged over other ethical perspectives. That is to say, no one ethical perspective can maintain that its ethical claims cannot be questioned, that they are in some sense absolute.

Therefore, your question appears to be attempting to put words in the mouth of the ethical relativist that are inconsistent with what ethical relativists believe. They don't consider the notion of "objective morality" to be substantiated by evidence.