As I understand it, they flat out refused to provide the same services to a gay couple that they provided to everyone else simply because this couple was gay.
Then you do not understand it correctly. The bakery offers a custom set of toppings. The couple asked for a topping that was not part of that custom set. In other words, they demanded something that was not on the menu. At no point did the bakery refuse to provide a cake because of the sexual preference of the customers (which is a private matter anyway and would be unknown to the bakers).
And as I understand it, that is against the law there.
Again, your understanding is in error. There is no Oregon law which forces a food establishment to sell something not on the menu. Which is why your statement about there being no Constitutional violations is pointless.
Too bad. They should have been more up-to-date on the laws that affected their business.
Perhaps you are the one who needs to be more up-to-date on the law since you are having a very difficult time identifying the law that was violated here.
Again, the couple was not denied service. They asked for a cake. They were sold a cake. But the bakery refused to provide a topping on the cake that they did not offer.
So back to the cupcake example. If I purchase a cupcake from a baker who refuses to put boysenberry icing on it, should they be required to pay me $135,000 at the point of a gun?