Actually, it is that simple. The grandparent made a false equivalence. Sexual orientation, color of skin, race etc. is not a choice that someone makes. Your political orientation is a choice you make. One of them is not the same as the other.
The false equivalence is in the original argument ("accountable to anyone"), that's what the grandparent was attempting to point out.
The equivalence the gp is making is between businesses, not clients. Businesses obviously are accountable to someone if they must serve gay people. It has already been pointed out that gays are a protected class, but deliberately(?) missing people's points has never helped a cause.
That's not what is happening, as I understood it. The grandparent simply refuted the general argument that "The business does not need to be accountable to anyone" by providing a counterexample whereby unconditionally following this argument can lead to an unwanted outcome.
In other words: it's not that simple.