Grammar more important than behaviour?

I keep catching myself in questionable child behaviour correction. I just did it again. This is getting to be a real problem for me. Focus, Mumma. Focus.

We have built a fort in the playroom and there are many different types of allies and adversaries at war here now. It starts out fun but of course sometimes certain soldiers or knights are unimpressed with other warrior types.

Máire points at Morris, who has just knocked apart the fortress with glee, and says with a terrible frown, "Him is a poopy pants."

And do I scold her for calling names? No.

Mumma says without any further thought, "No, honey. HE is a poopy pants."

Good grammar is essential to proper insults. Is that my message????