It's rude to point out someone's smell.
Dave is on the bus beside a sweaty, smelly man who keeps looking at him and making eye contact.
Dave wants to tell the man to stop looking at him.
"Dave looks up at the smelly man and says ""Can I help you with something?""."
"Dave looks up at the smelly man and says ""You disgusting, smelly rat, stop looking at me""."
The man replies No and realizes he'd been absentmindedly staring at Dave.
The man is angered by Dave's words and is also self conscious about his body odor.