The difference is that Nike is trademarked. If you did that, they could sue you. Then it would be up to a judge to decide if having that domain dilutes the trademark.
There are literally thousands of sites with similar names out there that deal with similar themes. Sure, some of them are just trying to piggyback on the success of others, but you know what happens to them? Unless the person puts a hell of a lot of work into them they just fade away.
If Webslaves new site was a complete mimic of KS, then there is an ethical issue there. But it's not, so the point is moot.
And whether a site gets 30 hit or 30 million shouldn't have any effect in the eyes of the law. If someone is trying to steal your customers/viewers through deceit/fraud, then big or small you have a case. There's no claim that they are anything but a forum for king snakes owners on WS's site.