Honestly, I think many of the reasons it would engender hostility boil down to two things:
First, Alliance is a game of stuff. A lack of stuff makes a character flatly unable to even use what's on their card and play at all, and much of the scaling is based on assumptions about what an average player has in their treasury.
Secondly, Alliance is expensive. Losing a character to PvP is flat out another player wasting a few hundred (or thousand) dollars of your time and momey when it comes to garb, props, and makeup. Not to mention how long it takes to regain build.
Given both of the above, I can't be surprised if PvP engenders OOG hard feelings. It isn't easy to stay philosophical when losing is a kick to the wallet.