Besides things already said in the thread, I'd also argue that the Soviets, despite being dicks after (and before), they did help defeat the Nazis and were the ones who marched into Berlin and took it over, and I'd say that their involvement in the war with the Allies was essential to Germany's defeat. Sure, if the Nazis never attacked them, they probably wouldn't help, but once they were pissed, the Allies were lucky to have such a force on their side. So, hammer and sickle sign is also, in a way, an anti-fascist sign (despite the fact that the USSR later on turned out to be ... close to fascism).
Also, communism in itself is not a bad or evil concept; it's actually too good to be true and it often twists into something else. In our sociology class, we learned that the main reasons for the fail of communism was the fact that it started in the wrong place and in the wrong time. But still, as an idea (as proposed by Marx and Engels), it's not an "evil" concept that proposes killing and oppressing people; it's good in theory, but it cannot be done in real life (at least not yet). However, Nazism is a form of Fascism and there's little to no positive things in it, at least for the majority who don't "fit" in. There's no "good on paper, mostly wrong in reality" in it, and Nazism is also keen on militaristic expansion and forcing its ways onto weaker countries, while communism is pretty much making countries closed and does not really effect others who don't want it (well, some of the Eastern European countries would probably disagree here). That's not better necessarily, as it oppresses people from the inside so people are less likely to turn on it, as they would if someone invaded them.
Since the end of the Second World War and up until 20 years ago, my country was a part of Yugoslavia, which was a socialist state. There are still debates over whether it was good or bad; some people are proud of it and say that it was the best we could have at the time and that it saved us (Yugoslavia was a pretty powerful country), while some people say that it was the worst thing that ever happened and still, to this day, rage on about "communism". We'll have elections soon and it's common to insult left leaning parties by calling them "communist". Of course, Yugoslavia's "communism" was not really communism at all, and while there were things like political killings and exiles, it was nowhere near like in the USSR. As a matter of fact, Yugoslavia's leader, Tito, officially declined to ally with the USSR and to condone to their policies (we had our own variant of communism/socialism [http://en.wikipedia.org/wiki/Titoism]). To this day, some people recall some of the socialist laws and solutions to many problems that we have today (for example, there was free college education, while we today have to spit out ridiculous amounts of money that are in no way adjusted to the average pay). Personally, I don't think our socialist country was extremely bad, especially for that time, but I also cannot agree with how many things were done. Over here, we somehow avoided the worst aspects of communism and I believe there's a hammer and sickle sign on some of the anti-fascist monuments (along with, more usually, a read star), so we don't really see it as something to be banned, and certainly not comparable to a Nazi swastika.
