Hmmm, yeah I think you are right.

I don't allow blacks in my restaurant is illegal. even if it is a real WANT.

I think this extension of the law to include sexual orientation is broadly applied in the USA, but it not (yet) a universal (federal) protection.

still for most of the USA it is.

and baking a cake is pretty similar to serving someone in a resturance.... similar. It is still a small step further, since most of the time the non-discrimination is ensuring that one is not excluding on the basis of being within the protected class. but in no way are you required to implicitly condone that class.

this is a step forward: you must also implicitly CONDONE the action of that class too.

it is a step beyond merely letting someone eat at your restaurant.