You don't have to accept biological males - you just say you are a ladies only salon.
A court case local to me determined that biologically male trans women using a local pub had to use the gents toilet after one of them used the ladies, a local complained and the landlord asked them to use the gents. They got offended. From memory it went to the European court of Human rights. The landlord won!
What upsets me about this story is that it could stop salons being trans friendly. I think the salon in question only advertise that they offer ladies Brazilian and are probably trying to make it clear that they welcome trans clients. Maybe they should clarify, but this could put a lot of salons off being inclusive and welcoming to the trans community. I definitely think the salon did the right thing.
Long ago I received a very rude email from a chap who took offence that I didn't offer male intimate waxing. At the time I worked on my own from home so offered no male treatments at all - nor did I offer female intimate waxing. We can all be offended if we go out looking for it, but this has made me wary of advertising that we welcome trans clients if we have to clarify the waxing we offer is for ladies bits only x