We weren't robbed of the title, no. Eboue did dive for the Free kick, and we might have lost with 11 men on the field anyway. Arsenal fans (and me) aren't really angry about losing, or feeling any injustice on that front.
It's the ref that we don't like, not because he 'cost us the game' or anything, but just because 1/ he was crap and 2/ he made the game that much less entertaining.
On the red card: You can't have the card AND the goal. Why? Lehmann got a red card for a foul when he was the last man. This only applies when his foul stops the other team scoring, when without the foul they would have scored. Since they scored anyway, the ref should have played advantage, given the goal to Barca. And as with all advantage rules, Lehmann would not have been penalised, certainly not a red.
And quite independent of the red card incident, he was just a horrible ref. Yes, sometimes to us as well. You might say "well it's okay then", but it makes the game much more cagey and much less open, flowing, entertaining. Henry got a yellow card for a tackle where he actually didn't even touch the other player, for example. I don't see how that is even possible.
Pretty much, Arsenal and its fans aren't "making a case", or saying we deserved to win but didn't. (I guess Wenger says that, but it's like the manager's job to say that every time any team loses now. ) At least, I don't think that. I just find it a pity that the refs many bad decisions made the game less entertaining for everybody, no matter which team they supported / played for.