IMO Killshooter is a necessary evil. Back in the days of AW DOS (the "grandfather of flight sims") there was no killshooter. Pilits would shoot teamates and countrymen down regularly. It was fun at times, and to a certain extent, it would discourage kill stealers. But many didn't care for it because it affected their K/D's, an important point which seemed to lead to some form of killshooter. Don't forget, HT and Pyro are former AW pilits, and perhaps some of their experiences and observations there, have formed their concept of our current flight combat sim here.
I don't care for kill stealers, and I feel badly when I do it myself
I don't intentionally do it but, it happens.
In the MA, there will always be the kill stealers, and if they try and are behind someone, they will pay a price for their greed. The downside is, when they have more E and dive down to steal yer hard earned kill, and you fire and die because of them. Because it is the MA, the odds are that it will happen to them too

This is why I like scenarios. The kill stealer doesn't do well in them because he/she will stick out like a sore thumb because there is a greater sense of teamwork than they are accustomed to.
In the MA its every man/woman for himself/herself. Its a tough place but fun most times. Either deal with it or, don't fly there.