I think hes fundamentally misunderstanding the 1st amendment. Specifically, congress shall make no law respecting an establishment of religion, or prohibiting the free excercise thereof.....

The government can't make laws against Islam (or any other, obviously) or stop people from practicing theres.

As a citizen, he IS entirely within his rights to refuse to acknowledge the validity of any or all religions, judge people for the parts of theirs that do not align with his own morals and beliefs.

His 'paradox' is that. He apears to be interpreting the first part of 1A as saying he both must and it allowed not to hold his own beliefs with respect to others religion.

He is even entitled to the opinion that 1A is wrong / immoral. And thats what its also saying. Just as the government isnt allowed to tell Muslims their religion is wrong, the government also isnt allowed to tell him that he can't say he believes they're wrong, ignore them in his everyday life etc (Free speech, association)

Now, like anything, theres limits (hate speech, discrimination if hes acting as a buisness, etc)

But quite literally, he could go around saying "I dont believe Muslims should be entitled to practice Islam in america" and the government can't stop him. Just as wed all be free to call him an asshole and say we dont believe he should have the right to espouse that opinion, etc.

The government is just barred from agreeing with him, or us for that matter. and obviously, everyone is barred from actually trying to enforce their beliefs on other people- the courts are barred from giving him a judicial path to that end, and theres no legal way for him to prevent Muslims from worshipping by his own hand, just as theres no way for us silence him, by design.