I agree with sizelocking. Set a maximum width using css and they'll get resized to it without proportions being busted.

The main problem in my opinion is that the gifs were getting turned into full post-width videos that I think everyone will agree was absurdly large. The rest seemed fine. But now that people have been annoyed by the post-width videos this troll has decided to be disgusting in order to get their way. It's almost certainly an existing member that wants the feature removed rather than any external attacker and they can fuck right off with that behaviour imo.