I believe you may have misinterpreted the poem. It's not about preventing "attacks" towards other extremists, it's about _suppressing_ them. It's one thing to argue with someone, fight with them, make your disagreements known, and whatever. That advances the conversation. It's a completely different issue to silence and suppress your enemies. That leads to authoritarianism, whether from the left or the right.

In my opinion, it is right of the majority to make their disdain towards the Nazis known. It is right of them to denounce their behavior. I personally don't feel it's right to suppress their ability to express their views, however.