I inadvertantly started up a firestorm a little while ago among some friends. We were talking about marriage in general and then the topic shifted to interreligious marriage. I said casually that I wouldn't marry a non-Jew unless that person converted to Judaism.
I didn't think that statement was a big deal--but one person exploded at me! He thought I was very narrow-minded, prejudiced, etc. Especially, he added, since I come from a mixed family myself.
That's true--and I'm glad I come from a mixed family. There are Catholics, Protestants, Jews, Unitarians, Buddhists and agnostics swinging around our family tree In fact, since Judaism comes down to me through my father and not my mother, for me it was a matter of consciously choosing to convert.
But I'd still only marry another Jew. Not that Judaism is better or worse than any other religion--but it happens to be mine. If I married, I'd want to practice it with my spouse. I'd want Shabbat meals and an active life together in synagogue. And I'd want to raise our kids firmly in Judaism.
To be honest, I think it's tough for anyone to marry outside their faith. If your faith matters to you, presumably you want a partner who shares it with you and who understands the road you're on. Not that mixed marriages can't work--I've certainly seen them work in my family--but it makes life more difficult. (And at the very least, I think you'd have to agree about how to raise the children ahead of time.)
Interreligious marriage is always a hot-button issue in Judaism. For example, Conservative synagogues now have the option of blessing homosexual unions--but only if both partners are Jewish! A Conservative rabbi still can't perform an interreligious marriage.
I know it's an issue in Catholicism as well--you can marry a non-Catholic, but they're supposed to promise to raise the children Catholic, etc. I don't know if it's an issue at all in Protestant denominations or among the Eastern Orthodox. At any event, though, I'd be curious to hear peoples' opinion on the subject.