As i said earlier there is no way for us to judge if someone is a true Christian or not. Someone you are judgeing to be immoral and dismissing as being sinner/kaffir/infisdel because of what you see as the normal lifestyle in the west, maybe a more pious person than you or I, maybe more dear to God that you or I. Can you afford to sit in judgement?
Of course a Muslim man marrying a woman of scripture will have to make that judgement call since it will effect him and his future children directly.
You said Muslim men are not allowed to marry Christian/Jewish women, which is the exact opposite of what the quran says, if you said women are not allowed to cover themselves in Islam, which is total opposite of what Islam says then I am sure someone will correct you there as well. Discussing Khimar is a minor detail not a total 180 from what the quran/islam says.