To be fair, the communist party did play a significant role in what led to the Nazi Party securing office, it's why we have this:
Of course the SDP isn't entirely blameless but that was a period in history where the communists inability to work across the aisle contributed to something pretty fukking bad. BUT, in general, you are correct, the tolerance of liberals has historically been the catalyst for fascist regimes to pop up. I mean, you can see it throughout the EU today, and you can see it here. If you don't eliminate that rhetoric with the arm of the state, which most EU countries attempt to do as they have hate speech laws, they continue to grow in power. The U.S. is one of the few countries that doesn't even regulate hate speech, and we are seeing a sharp rise in ring wing terror, domestic terror, and we can't even get bills passed to recognize this, let alone combat it. But I will say, if fascists succeed in this country, it's primarily the fault of the Republican party, although one could suggest that is what they want, or at least their constituents, just depends on who will take the mantle, Trump for example.