The hammer and sickle represent communism. Stalinism isn't communism. Communism is essentially an egalitarian society, and while no one has really successfully implemented it so far, this does not make it evil. Communism is the epitome of idealism and, as an ideal, it is wonderful but implausible.
The Swastika has been ingrained in the public conscience as the symbol of the Nazi party, which stood for a lot of awful crap that you probably already know about and that I won't bother to go into. Suffice to say, the evils committed by the Nazi party were an inherent result of the regime. Remember, the nazis also called themselves socialists, but anyone can see they weren't any more socialist than Stalin was communist.