it says 3,600 a year in new york; this does not sound like an esoteric fringe practice, but at least a sizeable minority

The only community that practices this archaic ritual is in NYC, so I'm not sure the specificity matters in this case. Let me also point out that the community is estimated to comprise 250K, "many" though not all of whom practice this. Avoiding granularity, there are approximately 7 million Jews in the US, which means this 250K community represents roughly 4% of all Jews. Given that (from what I gather) all examples of the practice are contained within this enclave, calling it "commonplace" is a mischaracterization at best. It is a practice held by a very small group within the broader community, which means calling this commonplace for Judaism is inaccurate. This is at most commonplace within a fringe group. My conclusion would be that outside of this fringe group, this method is not practiced by Jews at all.

>This is at most commonplace within a fringe group

If you describe the practitioners of this as a "fringe group", on what basis do you consider the comparison (not even identification) above to a (hypothetical!) "cult" offensive? And do followers of small religions which have been stigmatized with the label "cult" not also deserve the same respect for their beliefs and protection from discrimination as other religions?

I think my gripe is the same as all racist comments. Applying something that's true for a small subset to the whole group. If you want to be specific about what type of Jews support this practice, it's a very specific community of Ultra Orthodox Jews. I tend to fall on the side of all extremism being bad, so if someone wants to say the most extreme practitioners of a given religion are bad, then that's fine. But one should not don't talk about Jews as a whole when it is but a small subset within the Ultra Orthodox community.