First off, takes two to HO. You could have avoided going H2H with the F6, but you chose to shoot at him as well, hence you're now leaking oil by your own hand.
Don't expect pilots to give you a free pass just because you're greased a little. An oil leak by no means makes a plane disabled. Sure might be hard to see, but you CAN still see out the window and your guns WILL still shoot.
Personally I won't fire on a plane if he's missing a wing or on fire (although you get the occasional pilot who still tries to continue on while burning, in which case I will take him down to save allies).
If the wing's gone, that plane is pretty much out of the fight, and I'll let him go. I don't need perk points and I don't care about score, so me chasing down a disabled fighter does nothing more for me then trying to boost my own ego, which I don't need to do.
You'll come across a lot of different pilots in here. But truth is it's an online game....expect everything, and don't be surprised if people play the way you usually don't.