But proselytizing among Jews is also an essential part of Christian history. I would hazard the guess that at least through the 1st century AD a majority of Christians were Jews (I thought of saying "former Jews," but that is begging the question -- Christianity and rabbinical Judaism are both descendants of the Judaism that preceded both; they both regard themselves as the true successor of Judaism.)
How can you ask Christians to abandon that part of their history, especially when their theology calls on them to spread the Good Word?