Whether businesses can "legally discriminate" is subject to state and local laws. In Oregon, where the highest-profile case occurred, there is a law prohibiting such discrimination. Other states have laws preserving the rights of business owners to do so.
I don't mind having the debate as to whether those laws are morally right, but try to avoid making blanket statements that suggest that it's a foregone conclusion that those laws exist or that it's a foregone conclusion that those laws don't violate the rights of the business owner. Remember that part of the function of courts is to determine whether laws violate rights guaranteed by the federal or state constitution. Given that I believe that those laws are not moral and do violate the rights of business owners, it's not surprising that I would call the rulings ridiculous.
I believe that it is ridiculous to assert that my work is the property of another. Take religion or race or anything else out of the equation. To force a person to work, to create, against his will is slavery. It isn't the patron's right to demand service. That makes the worker a slave to the whim of the patron, forced to work or create not for himself, but because the patron demands it. Anyone who owns a business has the right to refuse service for any reason or no reason at all, otherwise he isn't free at all.
Laws such as the one in Oregon usually start with fine intentions. Unfortunately, the end result is that one moral right (the fair treatment of others) is somehow elevated over another moral right (the right to control and own the work of one's own mind and body). I don't know if anyone is qualified to answer which is more important, though if pressed I would say the latter.
I know from a practical perspective I would much rather let the free market handle this. If they willingly give up business because of their religious beliefs, then someone else will seize the opportunity and another bakery will grow. I wouldn't visit a business that I believed mistreated complete strangers for no reason, and I'm a straight white guy.
Also, you avoided my original point. Since doctors serve the public, are they required not to discriminate against the irresponsible by performing abortions on demand?