Avira, a good question about difference between metzitza and har habayit. I presume that the thinking is that danger is allowed when there is a reason. On metzitza, one can say that H’ will be also concerned about baby’s health and will forgive skipping this tradition. Gemora says that one Rav will postpone bris due to draft from wind, so it is not too outrageous to be concerned about remote threat to a baby. On the other hand, one might claim that going to Har Habyit has a value in strengthening Jewish presence in Yerushalaim, etc rather than danger. I understand that this is questionable, and that nonsense for you, but this is a disagreement on political judgment rather than halakha.
Looking at metzitza issue from recent knowledge, Aguda’s response that “driving is more dangerous” seems to be true. On the other hand, cases of post-bris herpes is still reported in press once in a while over the years. Maybe someone wants to compute numbers to compare with covid danger per person, assuming say 10 herpes cases per NYC (of course, cases may be under-reported).
We can also conclude that, similarly to Covid, it is possible that R Tendler with his understanding of builogy and statistics understands the danger and thus osers, while a community of people who do not study that may rely on “shomer peshayim”, as they do for Covid.