Person A does/says something.
Person B doesn’t like this and says so.
Person A says “let people do whatever they want”.
Essentially, Person A is telling Person B that they shouldn’t have done what they wanted (stated their opinion) because Person A does not like it, contradicting their own statement of “let people do whatever they want.” If Person A is entitled to do whatever they want, shouldn’t Person B also be? Only if Person A thinks so, it seems.
The more honest statement would be “Let people do whatever they want as long as I agree with it.”
Anyone who actually said that, although it’s more honest than the original statement, would appear to be a self-important asshole. So, they modify the phrase to avoid looking like the asshole they are. I don’t think it works, although it seems to be fairly accepted. Lately it seems that everything is bullying, even when it’s not. Disagreeing with someone is not bullying, neither is a person not liking something you like, not even if they tell you they don’t like it. If you like something, like it. Don’t be swayed by internet randoms. If someone disagrees with you, that’s ok. You don’t need to change your mind unless you want to.