Trevor Noah of The Daily Show points out how, because he is the leading candidate of one of the two major political parties, Donald Trump has given permission for people to say things that they may have formerly felt obliged to either suppress or only share with those they were sure shared their views. Now, pretty much anything goes.
Hasan Minhaj has his own theory of what is going on and his explanation is terrific.
(These clips aired on December 8, 2015. To get suggestions on how to view clips of The Daily Show and The Nightly Show outside the US, please see this earlier post. If the videos autoplay, please see here for a diagnosis and possible solutions.)