The doctors were discrimizing, being selective can only be done when there's a valid and objective reason to exclude someone, like denying a blind man a job as referee.
There's no evidence that gay couples make worse parents, the doctors convictions may be truthful, but that does make them intolerant (in the philosophical sense: 'tolerare' means 'to bear' 'undergo', they should bear the 'burden' of helping a gay woman get pregnant). We seem to have lost the real notion of tolerance, these days we confuse tolerance with disinterest. You can't tolerate that which doesn't bother you, but that's a side-track.
The unwillingness to treat the woman has no moral foundation, falling back on religion means that (with many religions around) people would have a lot of arbitrary motives at their disposal to refuse clients. Morality is a check of reason first, morality is religion/culture free, saying otherwise would lead to a very slippery path of subjectivism, which would ultimately mean that morality and ethics can't be advanced (which we clearly did, we abolished slavery, women got equal rights etc.).
