No, not all of those players are hackers. The players with "(Hacker)" behind their name are known to be hackers. Other names in this list are known as thieves, but some of them are just players who want to harass or be a trouble maker in general.
I am aware that several IT server forums got hacked by a few individuals. And it's quite sad that people go out of their way to destroy forums and communities that people have worked so hard on building. I shall let you know if I spot them around.