1. Thats why I keep 200 detuned. I don't care to see any lame crying from dead people.
2. If they PM you, offer to take them to the TA to show them how you did it.
3. If they challenge you to a DA duel, ignore them. They know you just killed them. I don't care to respond to such childish hair pulling.
Last tour, I repeatedly bombed a guy that kept coming at our town with a Flak pnzr. I would let him get close to town then drop eggs on him from a Mossie and kill him. After a couple times of this he PM'd me and said I had aimbot

I PM'd him back and offered to take him to the TA and show him how I dive bomb on GVs with a Mossie. It's called practice. No reply from him (imagine that).
As far a HO shots, sometimes you have no choice. Say you are flying a zeke or some other slow plane and some guy with a fast plane is BNZing you. You cannot get him to blow his E. He keeps screaming down on you at 450mph and you keep turning to avoid at 150mph. By the time you swing back to bring his plane into view, he is already 1k away and fading fast. Your only real hope is to turn into him and shoot him in the face on his next pass.
(Head on shots are mentioned in just about every WWII fighter novel I have....and I have ALOT of them. It was an actual tactic used by many and even perfected by a German squadron. One of the first well documented dogfight kills of a Me-262 that was shot down by a P-51 was done with a head on shot)
Prepare yourself for the crying that will surely ensue. He knows he had the discipline to not be lured into a turn fight and kept his E, he also knows there is no possible way you can play his game and E fight (your Zeke will compress at 400). He goes in holding all the cards and you end up wasting him....of course he is going to be sore. Ignore the crying.
Used correctly, it is a legitmate tactic. Using it as a primary tactic like on initial merge is lame. Using it for defence is survival.