Another recent incident involving (an apparently well known) comdeian Tosh-something which might point to a larger cultural trend as the culprit rather than a bunch of kids on 4chan:
A lot of comedy depends on reversal of expectations so the more political correctness is expected from people, the more politically incorrect jokes you will hear.
http://breakfastcookie.tumblr.com/post/26879625651/so-a-girl...