Don, they're right. As you have explained, you made and/or kept an alliance for reasons outside of that game, in order to improve your chances of making alliances in other games. That is metagaming, by the definition given at http://webdiplomacy.net/rules.php:
"You can't make alliances for reasons outside a game, such as because you are friends, relatives or in return for a favour in another game."
Further, the players and moderators of this site have determined that metagaming is against the rules, because it "gives an unfair advantage to those involved". So, yes, what Babak and others were telling you is considered by this site the only legitimate way to play.
I'm sure you can find people who will agree with your viewpoint, and there are several ways in which webDiplomacy is not the same thing as Allan Calhamer's Diplomacy. Nevertheless, webDiplomacy has made it clear that people with your views on this are not welcome here, and the owners and moderators of the site have the right to do so.
I should also point out that cheating allegations are to be kept out of the forums, so please don't accuse yourself of being a cheater in public. Instead, you should send an email to
[email protected], so they can take appropriate action.