I agree with all the posts. It really depends on how it happens. I had gifting my subs before knowing that I couldn't get 1st but since I was allied with two other players if I gifted them troops and specialists they would eliminate the competition and secure 3rd place for me. BUT I did not plan this from the start, we started out playing normally and all trying to win, we allied up and figured we could take top 3 spots, nothing wrong with this situation. And I think if you join the gsme (even with 2 friends) automatically knowing you are allies you will always start out by playing to win but if one of you falls behind without a chance to catch up you will support your allies. I would never join a game with allies and then just gift everything from the start, that's not fun at all and frankly unfair to others. To me, doing that would be just so you could get your rank up and get medals, unfortunately those are empty wins and show no skill, therefore they are meaningless.
As for multiboxing, that's just plain cheating, no respect for that.
All in all its just a game and you are dealing with human players and each had their own thoughts. The key is knowing who are your allies and who are the enemies and enemy alliences and try to anticipate such a situation. In the OP you say there are two other people helping this one player overtake you, honestly talk to your allies and stop him from doing that, and if it is just you without any allies then you took a wrong turn somewhere, can't win by yourself.