I was made to feel uncomfortable by a man on the bus when I was with my daughter, aged about 7 at the time.
I told him to leave us alone, and then said (quietly) to DD that it's OK not to be polite to people who make you feel uncomfortable.
In fact, it's not just OK, it's essential.
I am the first to shoot the breeze and exchange pleasantries with randoms, and my DC see me do this all the time.
But I won't be 'polite' or accommodating to people who make me feel uncomfortable.