Not disagreeing in the slightest.
But, in discussions where people ARE trying to prove something, then having actual evidence for opinions is a basic requirement, no?
Problem: "trying to prove something" and "opinions" don't go together.
Opinions are our positions or judgements we have formed that are NOT based on facts or knowledge. By definition, opinions will always fall short of being objectively provable. So, no, actual evidence for opinions is not required.