Freedom of speech means you can say whatever you want. What you can't do is lie, and then expect not to be held accountable for it. Not all opinions are equal and some things happen, just like we say they do. Slavery happened. The Black Death happened. The Earth is round. The ice caps are melting and Elvis is not alive.
I don't see any reason to be tasteful about Auschwitz. I say to you quite tastelessly that more women died on the back seat of Senator Edward Kennedy's car at Chappaquiddick than ever died in a gas chamber at Auschwitz.