Janet Smith makes the case that recreational sex and contraception are inherently inconsistent with natural moral law, here:
All she does is make a case that acting in accordance with nature is a good thing. Was anyone arguing against that?
However, not acting in accordance with nature is not, therefore, a bad thing. Her points regarding divorce, unwanted children, broken homes etc are entirely reasonable. They may well be the result of ill timed, unplanned and casual unprotected sex. But the problem is…ill timed, unplanned and casual unprotected sex.
I’m drinking a very nice whisky as I type this (a Glenmorangie if you’re interested). Now we all probably know that alcohol is one of the greatest problems facing society at the moment. If you suggested that drinking whilst driving or drinking until you are drunk on a regular basis or spending money on booze that should be spent on your family is immoral, I would agree. However, there is no way on God’s little blue planet that I would in any way agree that drinking whisky is, in itself, immoral.
Likewise, having sex just for the hell of it, just because you enjoy it, just because it feels good, if it causes no harm, is not immoral. It becomes immoral if, like anything else, it causes some harm.
Convince me that in a particular scenario that it would, and I will agree that, in that scenario, it would be immoral. That is, you need to start your argument with this:
Recreational sex is immoral if…
If you start it with:
Recreational sex is immoral because…
…then you have lost the argument before it starts.