I think he was just being an over-dramatic 5-year-old. My kids said some real gems when they were that age and have turned out just fine.
Yup, no telling what's been retained in the little tape recorders inside their heads. My sister, about that age, made up a story about a crab and used the word "obnoxious" in it. Nobody knew where she'd heard that word.
And I agree ... I think the kid's smarter than his mother.