That's not body shaming. It'd be different if they were commenting on their weight or a visible attribute. The pee pee in reference is (hopefully) in the driver's pants and OP couldn't possibly know what their pee pee actually looks like.

They're implying they have small dick energy, which describes a behavioral typology more than the actual size of a person's genitals. No one in this thread seems to think the honking driver could possibly be an impatient road ranger honking prematurely be cause OP didn't just kiss two fingers and look to their God before just sending it right into incoming traffic yelling, "YOLO!".