Saying Avengers fandom is the only one that goes that far is a huge stretch
Comic fans are that bad, umm I’ve seen Classic Doctor Who’ers get that bad, as well as video gamers and other Marvel fans. Not to mention how bad Sherlock fans get way too often. There are always crazy fans in fandoms that will get in your face for the slightest thing that they view as an offense. It’s not one fandom or another that’s worse than others.