The funny thing is (besides the last panel) is that how life works. Progressives have some good and some bad ideas, the good ones move politics to the left, so if you never adapt you become more and more of an extremist right winger. E.g. if your views on people of different colors are inspired by politics from a century you ago you are a racist and if your view on gay people are 50 years old you are a bigot. So yes, if you lack critical thinking skills to reevaluate your positions from time to time the political center will move to the left from your perspective and you will end up the racist/sexist uncle everybody hates and belittles.
OR you've made the mistake of only seeing one small slice of a curve and looking at its first derivative without being aware of the greater arc
Because historically, social trends of decadence, debauchery and radicalism have existed in numerous societies that swung to repressive, puritanical and regressive.
A time when orgies were normalized in Rome, a time when Iranian women wore bikinis. A time when Hollywood couldn't show too much ankle.
But sure if you look at an 80 year slice of American history you'd think societies always moves to the left and its inevitable progress. Just ignore the 2500 years of world history before it
Seems to me like a good reason for progressives to be more careful when pulling back on that pendulum