the unjust or prejudicial treatment of different categories of people or things, especially on the grounds of race, age, or sex.
Discrimination is not simply the unjust treatment of anyone, it is specifically the unjust or unfair treatment of someone based on the fact that they are part of a particular category of people.
Therefore, I am 100% correct in saying, "whether or not something is discrimination is entirely based around the motives of the person being accused of discrimination." If they refuse service specifically because of someone's sexuality, then that is discrimination. In this case, they are refusing service, specifically because in performing that service, they would be going against their own religious beliefs (celebrating homosexuality). That is not discrimination.
Not only that, the government literally discriminated against his religious beliefs.
Considering a gay wedding to be a "celebration of homosexuality" is an opinion though, and that is what makes it discrimination. In function, it is just like any other wedding. Refusing service because the wedding happens to between gay people makes it discrimination. No different than refusing service to an interracial couple. ---