I got called out by a red a couple of days ago while playing a btc as "Mercy -1":
I was playing German and was well ahead of my team mates with the reds mostly still at their ship. I flew wide, originally to try to draw the reds so the blues would have fewer defenders to face. I hugged the terrain and followed a line where if I got shot down I would be in tank range. One red crashed trying to get to me while another got suspicious and quit firing. I made an evasive loop rather than head out over the water. A red said "Why no bomb Mercy?" as I turned around and dropped him. I then made the short run across the water as he was respawning and dropped both of my bombs on the carrier...."Merry x-mas"...."I was saving them for you".
By that time the other blues were either on the carrier with bombs or had been shot down in range so the carrier took a quick 6 hits and the game ended. Its sad when someone is so sure that you're "cheating" that they take the time to complain instead of playing, then..... suprise!
In another recent game I got called out for "sneaking" while the reds were outnumbed. When I'd started my run the teams were even, several came in and left the game during my run. I think it was 3 vs. 2 when the complaint came. The funny thing is that my specific intention was to be in view to draw the reds off.... again, I was still carrying. "Sneaking"? "Outnumbered"? Come on...play the game. If I had dropped my bombs on tanks and then done this I sure they would have been certain that I was "cheating" even though no one would say it was wrong to bomb tanks... I suppose will say that I should have turned around to re-arm... bah!
The fact is there will always be those who play "abusively" and there will always be those who are ready to complain about how others play, and since there is no way to know for sure what someone else is doing or thinking there will always be lots of grey area when it comes to "ethics".
The harder you fight in-game and the less you worry about whether someone else is being "fair" the better the games will be.... unless of course someone just likes drama.