I think we can all agree that the sentence seems to be pretty light considering the offence, but I am not sure if it is unusual as I don't really have much experience in people that have commited assault occassioning actual bodily harm. For all I know it may be a standard sentence for that sort of offence.
From reading around the subject it seems that whilst racial insults were used the attack itself was not racially motivated, the girls being drunk and the interaction between them and the victim seemed to be what sparked it, not skin colour.
The Daily Mail, as per usual, is doing some pretty poor reporting trying to insinuate that it was because of their religion that they got off so lightly. Again this doesn't seem to be the case, it may well have been what the defense tried to use but the judge doesn't seem to have made mention of it.