Sure, junk yard dogs are mean but the meanest dogs are often found guarding concentration camps.*

*Early versions of the Jim Croce's 1973 smash hit "Big Bad Leroy Brown" initially included the line "meaner than a concentration camp dog" but Croce decided it was unpleasant to the ear. Also it was offensive to Jews, ♥♥♥♥♥♥♥ and homosexuals. Little did it matter though, Croce would be dead within a year.