If "hunting down" psychopaths is our goal, we'd do better to look for people who torture or kill animals. My understanding is that these behaviors are a common warning sign of antisocial personality disorder, and I'm sure it's more common than infanticide because it's less punished. Would you advocate punishing anyone diagnosed with antisocial personality right away, or would you want to wait until they actually committed a crime?

I'd put taboos in three categories. Some taboos (e.g. against women wearing trousers, profanity, homosexuality, or atheism) seem pointless and we were right to relax them. Some taboos, like those against theft and murder, I agree we should hold in place because they produce so little value for the harm they produce. Some, like extramarital sex and abortion, are more ambiguous. They probably allow some people to get away with unnecessary cruelty. But because the the personal freedom they create, I think they produce a net good.

I put legalized infanticide in the third category. I gather you put it in the second? In other words, do you believe the harm it would create from psychopaths killing babies and generally being harder to detect would be greater than the benefit to people who don't raise unwanted children?