True depression usually isn't just about "unprocessed emotion", often it is a chemical imbalance, hormone problem, thyroid problem or something else entirely. And I would say that those that commit murder or even suicide are in the distinct minority of those who take these medications. I think this issue is a whole lot more complicated than just "if you take an antidepressant you are going to kill someone or yourself". Clearly these medications don't help everyone to whom they are prescribed and for some it causes harm, but then that is true of every medication. That doesn't mean they don't help people.
This is definitely something that needs more study but to dismiss these medications as something that no one should take would probably do more harm than good.