He compares himself with others who drink far more than he does, and in his perception, this rationalizes that he is not that bad.
ىىىىىىىىىىىىىىىىىىىىىىىىىىىىىىىىىىىىىىىىىىىىىىىىىىىىىىىىىىىىىىىىىىىىىىىىىىىىى link