Wait until you progress farther in the game, he isn't too bad at first but he gets super emo at times, and he always has a depressed/moody vibe to him. At least that what it seems like to me.
Vivi gets picked on in towns sometimes because he resembles Brahne's Black Mages, so people are naturally going to be hostile towards him. Vivi's problem is that he never stands up for himself when people question him. If he would actually defend himself and speak up he would never have a problem with people. Of course, Vivi never does that because he's such a shy, depressed little thing that would never hurt anyone even if he was being attacked (Black Waltz 3 being the exception since Vivi is actually pretty awesome in that scene). See what would happen if he didn't takefrom anyone?
I see how that would be confusing, but as soon as he sees Black Mages he should immediately realize they're the same. It can't be anymore obvious that they're the same, yet he still questions it for a long time.
(SPOILER)Vivi isn't an advanced version, but instead a prototype. Luckily he lives longer than normal Black Mages do.
Squall being socially detached was his way of dealing with his problem. He didn't want to experience the same hurt he felt when Ellone left, so he chose not to become emotionally attached or rely on anyone. Fortunately he meets Rinoa who breaks him out of his funk.
Vivi only defends himself a couple of times throughout the entire game. The Black Waltz 3 battle being the most significant. He's more shy and afraid than he is courageous.
Courage? You think Squall didn't have courage? Squall shows courage countless times throughout the game. He confronts Edea and Seifer head-on without help, saves Rinoa several times (Garden battle, coma, space, sorceress memorial, etc.), and even enters time compression without any real certainty of what would happen. No courage? That's absurd. I do have respect for Vivi, but saying he has more courage than Squall? No.