The boos were certainly for the sub, not Arshavin personally. Although yes I can see how it could've been seen that way and that Arshavin may have felt dead inside after.

We as fans have been extremely patient, so frankly I don't care if Wenger, Arshavin, Henry or anyone else at the club feels the fans aren't pulling their weight. We see the same shit over and over, it's like every season is a repeat of the last.