At first I gave them the benefit of the doubt that they were just trying to be edgy online but it seems like they really do believe the baseless statements they say. I feel bad for them, they seem like they have a lot of hate in their heart.

Have you talked to your girlfriend about this? Is your girlfriend upset that you don't like the size, or is she upset that you won't wear the shirt (and you haven't told her why)? Because if it's the former, that probably warrants a larger discussion.

Not even getting into why this question isn't on the AITA subreddit but I swear most of these AITA questions could be solved by basic communication instead of asking some internet strangers what they think

I don't know, I could be wrong but I've noticed the rhetoric has significantly changed in the past 2 years to rethinking how much we fund those systems and how they are trained and vetted, rather than abolishing them completely.