This is not true. Reddit's political forums do not censor calls to violence against police for example (i.e. actual hate speech). At the same time they shut down the_donald while arguing that they threaten police (which is BS, since conservatives love the police).
The balance is currently that sites like Reddit allow a broad range of content, and have so far not banned a wide enough range of topics to push a significant enough fraction of their userbase away. As Reddit becomes more and more censorious, it might move beyond just banning literal white supremacy, into banning discussion other socially transgressive things. These might include drugs, technology linked to piracy, gambling, pornography and sex work, and a lot of other vices that are both fascinating (from the outside) and enjoyable (from the inside).
Reddit did not make a single choice on what audience to go after. It has made, and will continue to make, such choices every day it operates, and chasing revenue will cause it to ban more and more topics. Eventually, newer and edgier platforms will be able to gain prominence with a userbase of less political and more entertaining transgressors.