Who is a Moral Agent (in Gun Control Debates)?

One of the things that interests me about the debate surrounding gun control in the United States right now (recalling, of course, that this debate also appears in Canada whenever election time shows up) is that one of the most coherent oppositions to gun control is focused on the citizen's moral agency. Shouldn't the government focus on preventing actually destructive behaviour (murder) rather than preventing the conditions of that behaviour (gun control)? The role of the government is to produce an environment in which citizens are capable of virtuous action, not incapable of destructive action, though destructive action will be addressed, of course, in the criminal justice system.

I am immediately sympathetic to this kind of argument on two counts. The first is that I do really like moral agency; I get excited when people talk about taking responsibility for their actions. The second is that I like the idea of a state which is focused on helping citizens become virtuous agents rather than forcing them to be obedient agents. Lawful behaviour is much nicer when citizens are lawful for the right reasons rather than out of fear of reprisal. So the ways these particular opponents to gun control articulate their position is attractive to me.

However, I ultimately disagree because I subscribe to what I would call psychological realism. While I do intend to be a strong moral agent and to respect other people's agencies, I am at the same time skeptical that anyone's agency is non-compromised. In other words, I believe that people should take responsibility for their actions when they can but that people often will not and sometimes cannot act the way they should, even when they want to act the way they should. For example, I advise that you read this article entitled "Please Take Away My Right to a Gun" (trigger warning for discussion of suicide and the threat of home invasion), in which the author argues that she does not want to be able to get a gun because during periods of her recurring depression she would be tempted to use it on herself. Many commenters say that the author needs to take responsibility for her actions (and I've read some off-site comments saying that her argument is condescending toward the mentally ill), but I think she's just being realistic: she knows that sometimes she cannot trust her own decision-making processes and she knows that the current system will enable her suicide if she ever attempts it. She is compromised, she wants the state to protect her from herself, and I don't think she's wrong in believing this right trumps the rights of gun ownership.

But this debate has made me re-consider my own position on matters: is what I call "psychological realism" compatible with insisting that people's agencies be respected? One of the reasons I tend to shy away from anything resembling paternalism--particularly colonial paternalism--is that I believe it is intrinsically good to respect other folks' agencies (both to help them develop their characters and as an end-in-itself). But can I realistically continue in this outlook if I ultimately believe that we are all psychologically compromised? If the mentally ill are not full moral agents, how can I be one, either?