I do not want empathy-free sentient beings wandering about.

I do. At least as long as they behave. If you're intelligent enough to know (on an abstract level) why altruism and cooperation is good for humans within societies and have enough self-control to live by this principle, I don't know why empathy remains important. I mean, as a terminal value.

Slightly-less-empathetic people are okay but surely not more desirable than otherwise similarly intelligent empathetic people.

Empathetic, slightly-less-intelligent people are okay but surely not more desirable than otherwise similarly empathetic intelligent people. Punishing less intelligent people just because of this appears to be just as useless and (w.r.t. my morality) immoral as punishing less empathetic people.

I draw the line at outright criminal acts, I think.

I do this for the general population.

there's a tradeoff between the diversity of brains and the number of people murdered by psychopaths but I think we should probably worry about reducing murders first and then safely explore brain diversity once we understand brains better.

If there's a better approach to reducing murders by psychopaths than decreasing the number of psychopaths (by hindering them from reproducing, killing them, or other other suchs means), I'd opt for that.