How free can philosophy discussion be in the public domain?

This question is increasingly relevant to the way discussions are conducted, public and academic. This was particularly the case for the Same-Sex Marriage debate, in which it was suggested [here] that the debate itself was problematic. And the very same concerns have now entered into the universities, with a recent petition for a prominent anti-SSM academic, John Finnis, to be removed from his position for his views [discussion here].

These cases raise immediate questions: Is it wrong to SAY that heterosexual relations are morally superior to homosexual relations? Does it matter whether it is true or not? Is there an inoffensive way of saying such a thing? If not, is the offense enough to make it wrong? To mean that it should be illegal? How CAN we have this sort of discussion? But there are also broader questions: How can we discuss ANYTHING about which opposing sides feel very strongly, if at all? Is sincere offense enough to make speech wrong? How free CAN philosophical discussion be in the public domain? Or is real philosophical discussion just too dangerous in public places?