Because the child still has the right to not be of their parents' religion?

By law parents have the right to choose for infants because infants are not able to choose for themselves. If you don't want a circumcision for your child, don't get one but you don't get to make that moral choice for others. Also please stop with the hyperbole of "amputation" and whatnot, or this conversation is over.

Crying antisemitism or islamophobia is a cheap way out.

No its not, its a very valid moral concern of a law you'd implement. I don't see why it can't be discussed when I'm taking my time to discuss a minimally invasive procedure that can't be argued to have effects one way or another that constitutes enough of a reason to ban it.

And the problem with studying this is that there isn't a real way to compare, it's completely subjective to begin with, and people can't say which they prefer unless they've lived both circumcised and non circumcised.

I agree, which is why I think most people who are so against it really don't have much of a scientific base to stand on when they say it reduces pleasure. As a counterpoint, this article cited in the study you linked:

https://pubmed.ncbi.nlm.nih.gov/17419812/

claims that there are no differences in pleasure and sensitivity between circumcised and uncircumcised men. It was also not based on self reported data, but on sensory testing. As for how valid that is over the other? Who knows. That said, the article I linked was comprehensive in its data aggregate. While some said they regretted it, many also said they were fine with it and noticed no changes in sensitivity.

So that comes to my only point about this debate: It's not really based on science. Its more based on morals, and thats a fine debate. However, many of the against side are completely fine with brushing away any of the moral implications that could give them pause.