Rules? Laws?
He didn't murder anyone, you CAN'T murder somone over a forum. Nor can you steal or rape. It's WORDS, being permanently cut of from your freinds and a place that you love is WAY, WAY out of proportion even for the very worst thing that is is physically POSSIBLE to do through forum posts. There are bad things that shuld have punishments, but NOTHING deserves a complete blockage.
The forum is made out of bytes, there are no resources to steal or means to permanently cripple someone, it's a post sacristy economy, all the reasons that justifies law in the real world are invalid on the net.
Like other people have been saying: Yes, yes there are reasons.
For one, this is not a publicly-run place; it is privately owned and operated, and the people who own and operate it can decide what they want done with it and who can use those resources. They have that right.
And as far as justification goes, this is a forum. It's a social environment. A privately-owned social environment where the owner/operators will want to foster a certain type of atmosphere and culture, especially when it's built around something specific (in this case, an independent game developer's website). To state an extreme, if a bunch of neonazis started using it as their local hang-out and posting threads in General Discussion about various unsavory things and acting very very mean to everyone, it would drive people away, create a hostile environment, and be significantly detrimental to the purpose of the forum.
So yes, there are justifications for having rules here. It's a private community; "free speech" applies as much here as it does in my own house, which I also would have the right to kick you or anyone else out of if you annoyed me.