For anyone who's read the Drizzt novels, it's pretty well established that the people of the Forgotten Realms freak out when they see someone who looks like a monster (see the reactions to Drizzt). It's quite jarring that Tieflings are seen as anything but KOS monsters. Based on those books, you'd never even start a conversation with one. You'd just shoot the Tiefling on sight from long range (or flee).
