Objectively, I share your sentiments. I have limited on again, off again contact with another intensive, adult nerd hobby (War Hammer game with associated miniature painting. Others paint historical metal soldiers, play historical war game etc).
As you implied.... People whose social skills could use some uhmm...."enhancement"? We have those. People for whom the hobby is their sole consuming interest? Yes, they are there. Plain olde weirdos? Not unheard of- at all.
As you stated.... The group is nerdy but passive. None appear to have aggressive tendencies. They also accept all who have an interest in some aspect of their hobby.
I have seen an elderly religious conservative, a gender fluid person, and a guy whose T shirt implied that women are barbarian pillage prizes (wonders why he does not get second dates?) in the same small room.
Subjectively, however, I think there are some aspects of 501 Legion cosplay that could increase the chance of an unhinged participant:
- A former cosplay participant in a different genre stated that a when cosplayers get in deep, they get in very deep. A noticeable minority derived all their self respect, social status, friends, and even chosen family from cosplay.
- Dollar Cost. 501 Legion cosplay is expensive with the need for movie set costumes. If 501 legion ceases to "work" for somebody, they can be out what, thousands of dollars? And.... also out the prestige of being a member in the apex group. Other groups are out there, but are just not the same.