I hope its easy to see that the rise of this "cancer" and the alt-right was a natural response to the rise of the extreme left throughout popular media and in society in general.
There is nothing wrong with moderate conservatism, but when one must keep their conservative views in the closet, and anything conservative (on Reddit, Twitter, or simply at work) is seen as an inferior view point rather than just a different view point, then you will see extreme conservatism concentrated somewhere (in this case, 4chan).
There is nothing wrong with moderate conservatism, but when one must keep their conservative views in the closet, and anything conservative (on Reddit, Twitter, or simply at work) is seen as an inferior view point rather than just a different view point, then you will see extreme conservatism concentrated somewhere (in this case, 4chan).