Catechism said:
2358 The number of men and women who have deep-seated homosexual tendencies is not negligible. This inclination, which is objectively disordered, constitutes for most of them a trial. They must be accepted with respect, compassion, and sensitivity. Every sign of unjust discrimination in their regard should be avoided. These persons are called to fulfill God’s will in their lives and, if they are Christians, to unite to the sacrifice of the Lord’s Cross the difficulties they may encounter from their condition.
I like the way the catechism explains our ideal treatment of individuals with same sex attraction because it emphasizes compassion and respect. It also addresses your question of discrimination, reminding us that all signs of unjust discrimination must be avoided.
Note that it does not say that all forms of discrimination are to be condemned. There are times when we rightly discriminate. For example, we should discriminate, or differentiate, between heterosexual married couples and two men who are in a sexual relationship with one another.
With regard to the examples you offer, I tend to think of it this way: It is wrong to deny someone a service simply because they experience same sex attraction. It is not wrong to refuse to participate in objectively disordered actions or events.
If I’m a baker and a homosexual man comes to me and requests a birthday cake, I should not refuse him. If he asks for a wedding cake for his upcoming wedding to another man, I may see that as helping him to commit sin or participate in a mockery of a sacrament, and I can justly decline.
Every person should have the right to refuse to participate in that which they consider evil or wrong. If I, as a Catholic, approach a Protestant baker and ask her for a First Communion cake, she should be able to say to me, “I’m sorry, I don’t bake First Communion cakes. But please come back for your next graduation.” In other words, it’s not that I’m Catholic that she can refuse me, but that she doesn’t believe that she should help me celebrate something she believes is wrong.
So in sum, yes, I believe there are circumstances in which it is moral and perhaps even necessary to discriminate against same sex couples, but it is not out of hatred or disdain for the people themselves.