I want to know if you all think its morally wrong to bring a friend into a public game, without a pregame alliance

Friends generally work together (I say generally, some don't) and a lot of friends do it. It makes the game more fun for them, as they actually know someone. For the rest of the players, it is a bit of a downfall, but not too bad. It's only when 3 or 4 friends join a game together that it gets annoying. Because then, hey can take over the server. If you and a friend want to get together in a game, by all means go ahead. But don't close yourself off from other alliances, you may need to backstab your friend