Like they may start getting weak in the knees when they have to talk to someone at their school who drinks under age, occasionally skips classes, and who once tagged a mailbox with a marker.
In this case someone may need to just get more experience with the world and see that tons of otherwise good, nice people often skirt the rules in one way or another.
If we're shy, we may assume everyone is constantly looking for a reason to critique our flaws.
Some people come across as snobby and judgmental without intending to as well.
Some people feel uncomfortable around their friends' or partner's parents.