Yes it is fair because certain breeds have certain characteristics. These can often be trained out and say a pit bull will show no sign of reverting. However their is always a chance that circumstances maybe fear will bring out it's natural instincts. therefor it is fair to judge a dog by it's breed.
One of the snappiest I know is the white West Highland Terrier lovable in many ways but they can be snappy anad I suspect that if they were say black or brown they would not be tolerated.
I must confess i have been bitten three times and in each case it was my own fault and twice by accident when we went for the same toy at the same time
