because with mma and what not, there's an idea out there that you can look like bj penn or fedor or tim sylvia and still fuck shit up. brad pitt was 150 lbs in fight club, ed norton was 180ish in american history x, etc.
the "old" hollywood adage (that really only existed with arnold and stallone) that muscles = bad ass death machine is dead.
and as per usual, the ones who call brody a bottom twink should post their own pictures for comparison, but i'm guessing the fat pieces of shit won't do that.