That's your take and your take is a private one of which you are not offering a service to the public. While I don't agree with or celebrate bris it's not my place (unless the law provides) for me to deny a service I'm providing to the general public because I don't like what my services are being used for.
Whether it is legal or not (to selectively withhold goods and services if you don't like where it's going) is a separate question to whether it should be illegal.
For example, I DJ parties on the side. I was asked to DJ at a house that was a friend of one of my neighbors. The guy had a confederate flag flying and other paraphernalia I didn't agree with when I went to assess the site. I wasn't surprised because that neighbor (who passed away) had one too. Ultimately they all had a blast and talked about music and the stupid shit they did when kids. They knew I wasn't excited about that confederate shit but it did not get in the way of my offering my service and getting paid $500 for 6 hours of dumbfuckery. If I was really bent out of shape about it I could donate $100 to the black panthers or some shit.
If you were really bent out of shape about it, you ought have the legal right to refuse to DJ that party.