I agree that red card was highly controversial. Players caught offside are told to play to the whistle, line up and take a shot just in case the flag stays down. Van Persie wasn't doing anything malicious, he simply thought he was still on and took a shot. This sort of thing happens all the time. He shouldn't have even been booked for his 'challenge' on Alves in the first place. And to pour more salt in the wounds, UEFA has actually taken action against Nasri and Wenger for the complaints towards the officials:
Arsenal’s Arsène Wenger and Samir Nasri charged by Uefa over comments towards referee Massimo Busacca - Telegraph
And apparently, Gauirdiola is unimpressed with Arsenal's complaints:
Pep Guardiola mocks Arsene Wenger's referee complaints as 10-man Arsenal crash out in Barcelona - Telegraph
I wanted a better game, and I think it would have been had the official not decided to send Van Persie off. Tough break for Arsenal though, you guys drew the best club team in the world TWICE in a row during the last 16. Chin up lads, you're still within 3 points of United, maybe still a chance to keep the Premier League trophy in London.