People do not have the right to their own opinions.
Several times now, I've been involved in a debate with someone, and someone (often not my debate partner) will interrupt the flow of the debate with the plaint "they have the right to their opinion." This is usually in an attempt to dissuade me from continuing the discussion, on the basis that I should not try and violate their right to have an opinion by arguing with them.
The implications of this are offensive. Sure, people do have the right to disagree with me. But I hold my opinions for good reasons, and I am always willing to defend my opinions from arguments by others. To blithely say "they have a right to their own opinion" and expect me to thus respect that opinion is offensive! It seems to me that if they have no basis for their opinion, then they have no business sharing that opinion.
Now, if for some reason they don't want to argue with me, that's fine. They can say something along the lines of "stop arguing with me, I don't want to discuss this", and I will grudgingly back off. I don't want to say that everyone has to defend their opinions whenever I ask them to. I just want to say that they have an obligation to be able to defend their opinions. It's okay by me if people have different opinions than me. It just bothers me when anyone thinks that an opinion is a sacred thing, not to be disputed.