Luke, thank you for the straightforward question that is probably on the minds of many Catholics. My answer is a couple of questions in return... If a measure to stop bullying would  "condone a behavior that is condemned by the Church as a mortal sin"  then wouldn't the reverse be true: would  allowing bullying in school prevent behavior that is condemned by the church? In other words, are there fewer sexually active adult homosexuals for having been bullied as children? I would guess the only people who aren't sexually active because of bullying are those who killed themselves because of it.