When you see visual stimulus, it causes your brain to simulate that in your mind but it's not true that your brain is "practicing" that behavior. When you see or hear someone playing guitar, the same effect is happening in your brain. That doesn't mean that you can watch Stevie Ray Vaughan play "Rude Mood" 20 times and then play it yourself. Likewise you aren't going to turn into a killer no matter how many hours you spend playing GTA4.
On top of that, I think approaching the issue by telling people "think before you play games" is condescending and ineffective. It's like articles that say "think before you eat." Nobody reads that and says "Oh you're right! I was a mindless eating machine before and now I'm going to be more thoughtful." They think "Who's this jerk telling me what to do? I'm getting a KFC Sadness Bowl with extra bacon!"
You are obviously free to write whatever articles you want, I just found this one a bit condescending and also based on a false premise. It was clearly well intentioned and thoughtful, so I'm not trying to insult you or make you feel bad just express my reaction.
EDIT:
Also I don't play multiplayer FPS of any kind much these days but when I fire up TF2 once in a while I usually play the Soldier because it's most like the old Quake 1 days of rocket battles.