H3H3 is justified in outing keemstar; I'm surprised operation false hope wasn't included in his video. Keemstar would raid channels/streams of young/unknowing people with a lot of positive stuff to get their hopes up, before telling them to start trolling/harassing them. He also was associated with a gaming gambling website that was rigged, so there's a lot of really shitty things he's done.
If someones manic episodes revolve around god complexes and inability to discern reality, it's a wild leap to take Keemstars word on "lol he was just acting" after it all went to hell and he made his money. H3H3, idubbbz, and others have shown Keemstar sliding into their DMs acting like their friend solely to dig up dirt. The whole "but we were friends" thing sounds insincere, with evidence pointing to him being manipulative. The day before he dox'd Etikas mental hospital he slid into his DMs acting like his friend, and thus you see another pattern in line with what I've stated earlier.
You can say that about literally anything; your friends, celebrities, politicians. The people involved are extremely influential and powerful, if they're doing shitty things they should be outed to stop their abuse. Many extremely rich and powerful YouTubers were undone and grew into obscurity because they were outed as shitty people.