This topic reflects life in general, where there are no objective morals. You can choose to do whatever you want, regardless of how those actions affect other people, and deal with the consequences, good or bad. Or you can choose to do unto others as you'd have done unto yourself, regardless if other people will also live like this or not, and deal with those consequences, good or bad.
Personally, if I see a 1v1 in the MA, I will ask my fellow countryman if he wants help. If he doesn't answer I will usually stay out, but not always. How could you tell if he wants help, but maybe doesn't have a mic, or didn't hear you ask? Maybe he gets killed and then asks why none of the friendlies in the area didn't come to help him. IMO, I'd rather have a pissed off teammate who lived, than a pissed off teammate who got killed.
IMO, no one in the MA should be too upset about not getting a 1v1, or having a 1v1 broken up by another person, friend or foe. If you really want just 1v1's, then go to the DA and find a like minded mate.