People
Some guy hit my car fender the other day, and I said unto him, “Be fruitful and multiply.” But not in those words.
— Woody Allen

Behind the line May contain spoilers.
Our reading
An editorial interpretation.
The speaker describes responding to a damaged car with words that sound like a blessing, then admits the wording was different. The final qualification invites the listener to supply a vulgar alternative. The joke substitutes ceremonious language for an angry insult while keeping its sexual implication recognisable.
Context reviewed