There is no easy way to convince people who have an ideological disagreement with the playing of violent games. To do so, one usually has to do the research and have the person be ready to listen to said research. Feeding in articles that conclude to the contrary, even headline by headline over many years, may work with people you're close to.
Your dad's position may be ridiculous to you, but to really convince someone, try understanding their reasons for believing it (don't assume it is ignorance, it's often not that, but rather a different selection of information). I myself have understood that there is a more subtle influence at work with shooters that you might not notice, but that might change you slightly over many years. The thing about shooters is that they're very good ways of training your reflexes, and that has good and bad results.
The good: you get faster at responding in violent situations, over time. This is perfectly good in and of itself. However...
The bad: in violent situations, you are more likely to respond violently. This is partly because there is usually no "surrender" option in a game, thus training your reactions to only have the other option (this being more noticeable if you play for many hours AND regularly). Running away in games is all too often not going to work, so again you're given only one option - respond violently. And when you are used to that option in an immersive game, I think you could be training yourself into "kick ass mode" when that guy in the alleyway really does ask for your wallet. Now, in combination with "the good" of this, the violent response won't just be the default, it'll be an instant default that you can't think yourself out of.
Now, if you're a pacifist, this is not a good thing at all. If you're in a dangerous situation where running or giving over the wallet would be better ideas, then this is not good. So I can see a bit about what your dad says. Meanwhile, I can also see that a good mental resistance, a strong mind, and careful attention to the subtle influences of self-training through games, can all mitigate the negative effects.
In this light, I suggest that you come at him with an attitude that understands his position in a more complex fashion, armed with detail and empathy, and you may just change his mind. That is, assuming he won't leave during your discussion. That is always a risk with busy parents. In that case, a more Chinese water torture approach - tidbit of information by tidbit over years - will have to do.