The entire media landscape is quickly becoming little more than left wing propaganda, this of course includes comedy.
Would it be fair to say that a great deal of media and comedy have been left leaning for a very long time now.
I would argue just around how militant the media has become thus leading to comedy having to cow toe the line they as a crop set.
As Dunki posted above (George Carlin) who was a long time hero when I was a teenager. He was very left wing but I would imagine if he were alive today, he would have hit piece after hit piece hitting him on views that are very basic to making yourself self aware.
Hell John Cleese is leaving the UK as he's fed up with the state the media tries to get everyone to pick a side...
I don't so much blame comedians. It's a very hard gig to get into.
I very much lean towards the media and it's hit piece BS to having a major jab and people for just making jokes that don't toe the line.