Is it wrong to harm someone in order to stop them from harming others?

Try not to, but if you must then choose the lesser of the two evils. The problem with people is they usually want to brutally torture them just for kicks.

It doesn't take a genius to figure out the simple things, but all morality is so complicated not even a genius could get it all right on thier own.

I'd say choosing the least of all the evils is a fairly evident solution.

The best moral code so far is the religious one.

There is no "the religious moral code". Religions are just as bad at determining what their religion prescribes, and even within the same one they can't agree, let alone across different ones.