It's not about identity as much as it's a very poor way to try to convince someone.

Don't base your line of argument on a statement you know the other person will likely disagree with.

For example "You should play Pathfinder because DnD sucks", holds no weight to people who don't think that DnD sucks. In fact if they happen to like DnD, it undermines your argument, because if you disagree about DnD, aren't you also likely to disagree about Pathfinder?