It goes both ways though; if I ask a gay baker to make clitoris cakes I don't think he should have to do that either, we all have the right to refuse to work on things we oppose; surely.
There is such a thing as decency, I wouldn't expect my local baker to make sexually suggestive cookies for me, she would not be comfortable making them and it would be arrogant of me to force her.
EDIT: for those likening the service to race, it's not quite the same, unless you were talking about a white person being unable to buy a racist cake from a black baker. Which I'm sure we all agree is a fair thing to refuse service for. We have control of what we put into the world. Tolerance means being tolerant, it does not extend so far as to deny my right to refuse to create something I do not support (matter of what you should support or not is not the topic here), otherwise anyone can ask anyone to make racist/sexist shit and they have no recourse.