Arguments for banning circumcision come down to saying, “What Jewish people believe God told them to do - not just in passing but as the very sign of their people’s unique covenant with Him - is too horrible to be permitted.” That is like saying to observant Jews, “Your ‘god’ is evil, and so are you if you follow what you believe was commanded.”
One can easily see why Jews would consider this deeply insulting, and even threatening, since a reasonable next step is to conclude that evil people with horrible religious beliefs and intolerable practices should be eliminated.
Exactly right.
Exactly!
You merely neglected to mention that what is "horrible" is defined by G-d, which reduces the "G-d has ordered something horrible" argument to nonsense.