I think your feelings are normal, nor good nor bad, unless you let the game fool you and make you hate really. Try flying with friends and playing in opposite teams, you will see this not very diferent of any other competitive game although you're putting a stream of virtual bullets in his cockpit.
The real thing would be different, and I read lot of combat pilot stories. It was not a question of liking to shoot someone, but to shoot or be shot.
Peter Brill, german pilot in wwii, gave a conference in Barcelona, in spanish, and today he refuses to talk of his victories, because he feels respect for that dead pilots. You may find it in mp3 or I can give you the link.
There is also another story of a pilot who was shot down and had to eject at high altitude, but he opened the parachute too soon, a mistake. He saw the other pilot coming with his plane, and when he thought he was about to shoot him, the other pliot made several passes near him, making the parachute close every time until he was low enough to breath again.
And there are stories of dishonor in the air too, but coming back to topic, I dont think you are experimenting anything strange.
and you made me think , but normally i curse and hate when its me the one who is being shot