Its actually been studied: link
Summary: women find men more attractive as short term partners if they have facial scars, and do not view them differently in the long term. Men don't view women as more or less attractive.
I'm sure people say that scars themselves don't look nice, and think people would look better without them. However, they don't change how attractive we find the person -with- the scar. It's a bit like if you imagine your dream guy, and his arm is in a cast. Is he suddenly ugly? uh, no.