Alterman doesn't actually know any conservative Christians, but he's qualified to defame them any day of the week.
I'll add my voice to others here. Conservative Christians are the best friends Jews have in this world. They are, in Alterman's terms, "philosemitic". They support Israel, come what may, and they love Jews. Most especially, it should be pointed out, believing Jews.
Alterman probably forgets that French Jews were rounded up and loaded onto the cattle cars by Frenchmen.
And as others have pointed out, Alterman probably forgets that while he is trying to dial in the precise gradations of anti-and-philo-semitism among Americans he doesn't know, there are people determined to wipe the Jews from the face of the earth. They have the will, and they are determined to find the means. It won't be Alterman or his friends standing in the gap for Israel and the Jews, it will be the Christians. The ones he doesn't know, but feels free to defame.
Out of curiosity, have you ever seen Au Revoir Les Enfants? A beautiful French film about Jews being stowed away and hidden in a Catholic boarding school. Really touching film. One of my favorites. You just mentioned the whole French cattle car incident and it came to mind.