I think people are entitled to dislike what they wish. However, when a person sets out to disenfranchise or marginalize a group of people because they take part in activities to which he has an aversion then there's a problem.
Although straight people have every right to find gay sex disgusting - and it's probably not something that they can really help all that much in the first place - they can not - or at least should not - be able to threaten us with violence, kill us, harass us, deny us employment solely on the basis of our being gay without consideration of our qualifications. It'd be nice to have straight people find our characterizing activity pleasant or at least not unpleasant, but that's simply not something which we have any right to expect or to coax out of them.
Simply, this issue of disgust is neither here nor there as far as the matter of discrimination is concerned - save in the sense that disgust is the impetus of the discrimination.