I answered yes.
Admittedly there are people who will miss-use it, but not doing aikido will not stop them doing other dangerous martial arts, fighting or even carrying weapons.
I have seen many thugs converted by Aikido, and it usually happens after a couple of years when they finally get to use the techniques practically (many thugs leave before they get any practical value from aiki).
I think the responsibility over someones safety when you are training becomes natural, and they start to feel responsible to others. In addition they get to realise that the smallest weakest looking people are sometimes the ones that can beat you senseless - so they are less likely to start fights.
For me aggression comes from misconception (often the feeling of a misperceived threat). Studying a martial art gives more confidence in yourself, and gets rid of the feeling of having to prove yourself physically. Maybe that is why I have never been attacked by a martial artist with any real experience. [though I can't speak for everyone].