History has plenty of examples of people who are willing to do harm for a good cause and end up just doing harm.
Yes, but keep in mind the danger of availability bias; when people are willing to do harm for a good cause, and end up doing more good than harm, we're not so likely to hear about it. Knut Haukelid and his partners caused the death of eighteen civilians, and may thereby have saved several orders of magnitude more. How many people have heard of him? But failed acts of pragmatism become scandals.
Also, some people (such as Hitler and Stalin) are conventionally held up as examples of the evils of believing that ends justify means, but in fact disavowed utilitarianism just as strongly as their critics. To quote Yvain on the subject, "If we're going to play the "pretend historical figures were utilitarian" game, it's unfair to only apply it to the historical figures whose policies ended in disaster."
We already have a situation where we can cause harm to innocent people for the general good. It's called taxes.
Since I got modded down for that before, here's a hopefully less controversial example: the penal system. If you decide that your society is going to have a penal system, you know (since the system isn't perfect) that your system will inevitably punish innocent people. You can try to take measures to reduce that, but there's no way you can eliminate it. Nobody would say we shouldn't put a penal system into effect because it is wrong to harm in...
Another month has passed and here is a new rationality quotes thread. The usual rules are: