I have trouble believing the extent to which AHII is a niche interest. First of all, WWII FLYING!!! Second, IMHO it is the best combat flight sim in the genre. Made by a small team dedicated quality...it is equivalent to craft beer. I consistently recommend this to anyone with an interest in online games.
Learning curve + input device cost (yes I know there are some terrifying sticks that fly with a mouse. You're freaks, get over it) + pretty much sandbox style gameplay means it's different from 95% of the other games out there. I personally think the main reason it's a niche game is the lack of direction it gives you. You're free to do whatever you feel like doing, and that leaves a lot of people doing the same thing every day and getting bored.
As to why we can't all get along, combine combative gameplay with anonymity with egos... You get what you see in the MA every day.
Although to be honest, the channels in this game are nothing compared to most online games I've seen. I had once seen online console chat described as a bunch of teenagers communicating via homophobic racism. I thought it was an exaggeration til I saw it for myself. We have it good, folks.
Wiley.