In 1660 the Puritans in the Massachusetts colony executed a woman by the name of Mary Dyer for the heinous crime of having a different religion than theirs. Is this worse than the Witnesses? It's not that simple.
I view things on the basis of not just what a dictatorial group is and does but what they could become if allowed. The Watchtower would be executing people if they had sovereign territory - a country of their own.