Some could be in denial of thier own issues and not realise they are as ill as they are- like they think people who self harm are "worse" than they are cos it's a way of seeing themselves as less "messed up". Also some could be lying to hide thier own self harm, or yeh just ignorant- maybe the person running the group should mention other forms of self harm that the other people probably do that they don't realise is self harm- drinking to excess, drug use, fighting with people, over eating, isolating themselves, gambling too much etc. I find I am generally one of the "most messed up" people in groups I go to, like most people had a good home life or good friends or whatever whereas I happen to have had a big range of issues including self harm so I get why you would feel bad about it. What I mean is they tend just have one instance of abuse or just mental illness or one incident yet I have had a lot. Most people take that as competing when I say that so please don't it's just facts lol.