Men should not have sex with women they are not prepared to marry and have children with. When a man has sex with a woman, he runs the risk of becoming a father and incurring all the obligations, rights, and responsibilities that come with that. Birth control can fail, and women that say they'll have abortions or take Plan B may change their minds in the heat of the moment, making the man a father. The only sure way to prevent this is abstinence from PIV sex until you've met a woman you're willing to marry or have kids with. If one or both of you aren't fertile, this obviously doesn't apply.

Biology isn't fair in this way. A lot of you are probably going to flip things around, and say that women shouldn't have sex unless they're willing to become mothers. Sorry. Things don't work like that. Women incur the risk of pregnancy by having sex with men, but that doesn't always have to lead to motherhood - there's abortion and adoption for the ladies.

If most men did this, there would be a hell of a lot fewer problems with unplanned pregnancies, regretful sex, and all the other risks that come from casual sex.