Who is “they” and where would they take them? A source for this claim would be nice, too.
See the link in post #17 of this thread. Short version: as late as the 19th century, the governments of some Italian states would confiscate Jewish children from their parents if someone (typically a servant) claimed to have baptized the child.
http://en.wikipedia.org/wiki/Edgardo_Mortara
http://www.davidkertzer.com/book/export/html/24
“Although such kidnappings were not uncommon in Jewish communities across Europe, this time the political climate had changed.”
The Jewish community has long memories - so it is hard to dismiss it as just a sprinkling of water by well meaning Catholics when just a couple hundred years ago it was a means used to kidnap children away from Jewish parents.