Because they're cutting off heads, cutting off arms, burning people alive, hanging people up in basements, burying people alive in boxes, targeting Protestants and Catholics for kidnapping, torture and murder, gang raping women for being "Polish Ground Observers;" and just for added effect, they're openly Stalinists:
What fun for a propaganda free for all: Neonazis vs Stalinists. Who is the most historically ignorant? Who can be made to look like the worse scumbags?
I suspect that many of the neonazis in Ukraine know little more about the Nazis than that they were anti-communist. Which does not say much about the teaching of history in Ukraine.