I held the opinion (and I could be wrong, of course) that perhaps it's better, whenever possible, to ensure that when non-Orthodox people get married that a proper, kosher wedding is performed (such as serving as witnesses to the ceremony - kosher witnesses being a condito sine qua non for the ceremony).
My disputant took the opposite position - that we should not ensure that they have proper marriages. I don't know if he would have gone so far as to say that we should actively discourage halachicly kosher marriages whenever possible, but based on his reasoning, I think he would have even agreed to that.
His primary concern, which is a valid concern, is the issue of mamzeirus. As we all know, if this woman were married in a halachically valid ceremony, and then were divorced (and, in all likelihood, there would be no get or an invalid one) then any children she had from any subsequent marriages would be mamzeirim - unable to marry anyone in the community other than other mamzeirim or converts (and their children would be mamzeirim as well).
I agreed with his reasoning that this is a concern; but I felt that there were too many possibilities that would reduce mamzeirus to a negligible concern:
- First of all, who says that they are going to get divorced? Yes, there is a high divorce rate (my disputant provided the customary 50% rate, I wasn't so sure that that was really accurate), but then again, even if they get divorced...
- There is the possibility that she will get a kosher get. It's not unheard of, of course. I have a relative who was in such a situation - she got married by a Conservative Rabbi (who didn't know what he was doing because he married them on Chol HaMoed!) in a ceremony that was, in all likelihood, not k'das v'k'din. Later on, when they split up, she had become Orthodox and was able to get an Orthodox get so that she could remarry if she wanted to.
- Then there is the possibility that she will not choose to remarry OR the possibility that her former husband will die before she gets remarried (or has kids from that subsequent marriage).
- Lastly, there is the question that if she remarries, will she have kids? Will she marry in enough time to have kids (before her biological clock runs out)?
My argument in favor of a kosher marriage was that you'll be saving the couple from having illicit relations. True that other, more serious prohibitions (such as Niddah, for example) will be violated -- but they're going to be violated either way - there's very little help for that (short of getting her to accept Taharas HaMishpacha - a tough sell for someone non-Orthodox). But just because they have the more serious prohibition of Niddah doesn't mean that they shouldn't have to violate the lesser prohibition of illicit relations. By "preventing" them from having a kosher marriage, you are causing them to violate today for a situation in the future which may or may not happen.
My disputant went on to mention that Chazal seemed to want to take whatever steps were necessary to reduce mamzeirus. And that despite the mitigating factors that I presented above, there remained a chance of mamzeirus and therefore we shouldn't do anything that would increase that probability.
My counter argument to that was that if we are concerned about preventing any possibility of mamzeirus, then we should simply abolish all marriages to begin with. If no one performs kiddushin, there are no marriages and then (barring cases of incest) there is no mamzeirus. Of course, I wasn't seriously presenting this as an option, but merely to show that the idea that we should do anything and everything to prevent any chance of mamzeirus is fallacious.
Of course, there is the opinion (was it R. Ya'akov Kaminetsky? - I'm not certain who) that if we see a couple living together as man and wife, even without the benefit of a valid kiddushin, they have a chazakah as a married couple and would require a get anyway. I'm fairly certain that R. Moshe Feinstein holds the opposite opinion (I'll have to listen to the Rabbi Frand shiur on that topic again).
Of course, I am not a posek and neither was my disputant - it was just a back and forth conversation that we had. Anything that either of us said could be off the mark halachically. I'm curious as to what other people think.