That seems to be the way of the Internet. Though, I don't know if they delete posts that make them feel "guilty," so much as they delete stuff that makes them think. Then again, maybe that momentary act of thinking is the source of their guilty feelings: for a split-second, they realize that all of their forum-based socialization is at best, a waste-of-time, and at worst, a pretty disgusting circle-jerk.
(Note: I know that some smart-ass is going to ask "Isn't that what happens on this forum?" I'd say that this forum has veered towards that at times, but when I log on here, I usually end up learning something, or at least having to think. That constant niggling question is definitely a great motivator for keeping the forum "clean," however.)
Unfortunately, I can't read anything on that board you posted, but I can't imagine it's that different than what I've observed on other such websites. Best of luck!