Read at least a little history. The SDP and German Communist party fought valiantly against Hitler, right up until the enabling acts were forced through parliament (and that only succeeded because the Communists were evicted before the vote). The German left fought street battles against the brown shirts trying to prevent their rise to power.
The Nazis were way more committed to what they were doing than the US Government is. If the dissenters in the US (I'm looking at you, Occupy) showed a fraction of the resolve that the Weimar left showed, we'd have cleaned house by now.
Even after Hitler came to power, leaders in the one place there was still some free speech -- the independent churches -- continued to voice and rally dissent. German intellectuals fled the country and loudly protested the Hitler regime from around the world.
The first concentration camps were set up to detain Nazi political opponents, they were only turned to the purpose of ethnic cleansing in 1938.
You frankly don't know what you're talking about.