You make a good point but humor is not exactly universal.
What's funny or amusing to one person isn't funny at all to the next. How are you going to decide fairly who is entitled to post which pictures?
You may argue that you're not talking about borderline pictures but once you set rules for that thread, you're going to create problems.
Mods seem to take a blind eye toward these pics lately
That's not new, though. Remember posters like mirkaland or nolefan? They were given a lot of freedom in that thread too and a lot of people complained about them not being funny either without moderators intervening.
It's difficult to draw the line and do it fairly.