OTOH neither a wedding cake,flowers nor photographs even remotely resemble a "human right" and,therefore...given the basic amorality of their lives...a provider of such services absolutely has a moral right to refuse to serve them and,therefore,should have the legal right to deny them services.
Morality and legality are two different issues and one should not dictate the other. The owner of an ambulance service may have a moral obligation to help a pervert as you say but that does not mean that morality should be law. I believe homosexuality is immoral but I do not believe we should have laws against. Speeding is illegal but not immoral. Morality is the realm of religion and individual conscience. Laws are the application of state power to maintain an just society. They should be not intertwined.
A bakery or photographer is just saying they would rather not enter into a contract with the buyer from the get go.