It was all going famously, until, in response to something or other, Charlie said, "Well, that's just stupid."
Taylor's eyes got wide, and he looked at his dad and tugged on his sleeve. "Dad," he whispered urgently, "He said 'stupid!'" This was obviously something of a shock to him, based on his reaction.
My brother regarded Charlie with a grave and disapproving expression. "Um, we don't say 'stupid,'" he informed him.
Charlie looked puzzled. "Why the hell not?" he asked incredulously.
"Because it's not nice," he explained. "Calling someone stupid isn't nice, so we don't say 'stupid.'"
Taylor nodded in agreement.
"We don't say 'stupid,'" Charlie repeated.
"That's right," he confirmed.
Charlie thought about that for a minute.
"Can we say 'fucking retarded?'" Charlie asked.
From what I've seen, my brother never tried to censor Charlie again.