How the Good can be Worse than the Bad

I'm trying to finish a paper that I started a while ago and have not been working on for a while. I don't normally do that. What is different this time, is that I'm struggling to find a solution to the problem that I intended to solve, which is the following: let's say we could make people morally good by applying some simple device, like a morality pill: you swallow it and then you will be free of all anti-social impulses and will never (want to) hurt anyone again. If we gave this pill to everyone, the world would be a much better place, wouldn't it? No crime, no racial killings, no child abuse, no rape and torture. We would all be good simply because we would be incapable of evil. Now what is the problem with that, if any? The problem is that some people, including me, have this weird intuition that something important would be lost in a world in which people were incapable of doing anything bad. As if the very freedom to do terrible things to other human beings were more precious than the state of being good. What I haven't quite figured out yet is why exactly that freedom should be regarded as so precious that it is better to allow the occasional atrocities that humankind is prone to committing than to be without it. My intuition is that it has something to do with human identity and dignity, with the way we understand ourselves, as free agents and moral subjects, as ends rather than means to an end (even if that end is morality itself, or a world without human-caused pain). But at the moment my grasp and understanding of this is fuzzy at best. Has anyone got an idea? Or am I completely on the wrong track when I feel that there is a problem here?