I completely agree that we should be aggrieved. Any time an important decision goes against you you should be aggrieved, and I'm absolutely fuming about the decision believe me.
I don't think we should just put it down to bad luck though, and say we did everything right and couldn't have done any more. We could, clearly. Let's be honest, if everything had happened as it did but the flag had gone up, we would have been thinking it was lucky that the linesman had got it right. Mistakes happen all the time, we know that. We should have conceded penalties in both games against city and against palace, we shouldn't have conceded a penalty against stoke. The fact that the decision was wrong shouldn't stop us from looking at what we could have done differently and Roberto's interview (rightly or wrongly) gave the impression that he felt that was unnecessary.
As an aside, the team that was on the pitch at the end of the game had 2106 Premier League appearances between them. There's god knows how many cup games, games in other leagues and internationals to go on top of that. Yes we have some young players, but putting everything down to inexperience just doesn't wash.