I don't think fascism is a real problem on the net and I know some popular places they are around. It got some reactionary traction in the last years, but they were derided and made fun off for years before and they never made significant inroads.

What really helps and has helped them is putting people und general suspicion and restricting user rights. That massively helps fascists. The increased content control is a major success fascists had achieved the last years even while not in power.