"That's a foul!"

[Rich]

It wouldn't get more than a little chuckle from me. And I'm certainly not shy about serving tea when necessary.

[Adam]

At most, it's a request.

[mbyron]

I wouldn't T up the kid till after I'd told the coach to control his bench. That calls the coach's attention to the misbehavior and affords him the opportunity to deal with it.

Doesn't work in every case: sometimes they're so far over the line you have to address it immediately. But in this case, if it's becoming a problem, that's how I would start.

[just another ref]

"C'mon ref, lighten up a little." I'd have to hear how it was said, but that doesn't sound like a problem. Could quite possibly even be said in a friendly manner.
But a kid repeatedly yelling for any call from the bench is not acceptable, in my opinion. If he sees something and spontaneously yells it (e.g. That's a foul!) I can live with that. The kid in my situation was repeatedly yelling for the 3 second call, and laughing about it. Coach had opportunity to stop it. He didn't, so I did.