Mikvah (Once More)

I was walking through Lincoln Center tonight, when I suddenly realized something:

Among the rabbis I've spoken to about making single women's immersion in mikvah permissible (thus making pre-marital sex not punishable by karet), the main arguments is that it would appear that rabbis are condoning pre-marital sex* . When I counter that the risk of doing so is less problematic than the current situation, when loads of observant Jews are breaking nidah drabanan (since foreplay without mikvah is forbidden derabanan) and definitely deoraita (no sex sans immersion, possibly no foreplay sans immersion, depending on who you hold by).

The response I usually get is two-fold: 1. Most single Jews are shomer** (I believe this is false, but don't know the statistics) 2. For those Jews that can't handle shomer laws (which become mandatory as a result of the ban on women's immersion), let them sin - it's not uncommon for an observant Jew to have one halacha that he habitually slips up on. Better for the few to slip, than for the rabbis to make pre-marital sex not punishable by karet, which might cause many to sin.

This counter-argument is false on two grounds: 1. Since most are already sinnning, you're just downgrading their sin from derabanan to deoraita. There is a long rabbinic tradition of not imposing halachot the community en masse will not be able to observe - and shomerness/continuation of the single women ban violates that tradition. 2. Pyschology shows that humans do not like living with cognitive dissonance. So while it is possible that an observant Jew will say, "I am observant but happen to be violating the set of sexual halachas, despite believing in them, because they're too darn hard", what is more likely is that, in order to lessen the dissonance, the person will either stop breaking sex halachot (unlikely given the strength of the sex urge in humans) or just stop believing in sex halachot - perhaps by just giving up belief in the halacha system in general. Furthermore, even if one believes in the halachik system, one might not like the feeling of hypocrisy inherent in "I believe in a system, but only observe part of it, cause the rest is too hard", and thus, prefer to simply stop observing the system altogether.

For these reasons, I truly feel that allowing single women to immerse in mikvah is an example of "Et laasot laHashem, hefirut Toratecha" - It is a time to get rid of one halachik prohibition, less the strength of that prohibition, cause Jews en masse to stop observing the entire corpus of halachik laws.

* My proposed solution to this was either a) takanah making pre-marital sex (PMS) forbidden b) statement condoning PMS c) making boys/girls take neder at bat/bar mitzvah not to engage in pre-marital intercourse - I was told that a neder wouldn't work because people would break it. Of course, by that logic, no halacha will work, because people might break any halacha - whether the halacha is not to go against a neder, or not to fornicate without going to mikvah. Note: My neder would be against pre-marital sex, not mentioning other forms of touching, such as hugging, kissing, etc.
** While there are Jews who are legitimately shomer, many claim to be so without actually being shomer. This group can be split into two camps: 1. The group that tries to live a shomer lifestyle, but occassionally slips up 2. The group that habitually engages in romantic physical contact. It is true, that many faux-shomer people don't engage in pre-marital sex, for religious reasons - but the same can be said of many openly non-shomer observant Jews.