Dude just walked straight up to her too while she was talking to someone else. I assume that these things have some sort of line? But nobody did anything until she reacted to push him away? He looks big as well. If he wanted to hurt her, he would have broken her before anyone had time to do anything. And anyone who is at Twitchcon knows there are cameras everywhere, especially at a meet and greet with one of the largest female streamers on the platform. You're not well if you just walk up to someone and do that anyway, but when you know you're on anyone on a dozen cameras and you still do it? That's not a sane person.
Also guy that pushed him away just has a big nametag pass on him, doesn't look securityish.