I don't know why I keep posting on this thread, but here goes. People keep asking for some anti-semitism 101 education, so in case anyone genuinely wants to understand and isn't just baiting, here goes. I will use circumcision as my example. Some, not all, anti-circumcision rhetoric comes across as anti-semitic to Jewish posters. This is because there's some historical background you may not be aware of. So here goes my explanation of that background.
To quote from my synagogue library's copy of 'The Covenant of Circumcision- New Perspectives on an Ancient Jewish Rite' : "Stories of Jews who died for the difference marked by circumcision are part of the general Jewish cultural repertoire. These stories range from the legendary martyred mothers of Maccabean times who knowingly invoked death by insisting on circumcising their sons, to recent memories from the Nazi era."
Those who describe circumcision as child abuse and who use emotive words like 'barbaric', 'mutilation', 'bloody', or who bring up the (very fringe and uncommon) metzitzah b'peh ritual are unwittingly playing into a long tradition of anti-semitic tropes around circumcision. As far back as the mediaeval era, depictions of Jews as 'foreskinne clippers', are common. These rumours were related to the famous Blood Libel, which says Jews want to take the blood of Christian children. We were supposedly so eager for children's suffering that fears Jews would kidnap Christian children to forceably circumcise them or take their blood were a common cause of pogroms. During riots against Jews it was very common for Jewish children to be taken away from their parents and raised as Christians, supposedly for their own good. The case of Edgardo Mortars, a Jewish boy kidnapped from his parents by the church in Italy in 1858 shows these incidents continued for hundreds of years. Indeed there is a group "Hidden Children if the Holocaust" composed of Jewish people who were saved during the killings but whose identity was hidden from them by their adoptive families and who only found out their origins as adults. When people talk about how Jewish parents are abusive or should not be allowed to circumcise their children, this sparks a real fear that their children would actually be taken away.
This painful history invests circumcision with a powerful cultural meaning distinct from its important and related religious role, which I can try to explain in a second post if wanted (sorry for the wall of text)...