To T or not to T?

[Hawks Coach]

Teammates commenting quietly, without profanity, on the quality of a call to one another doesn't rate a response from a ref. I think it makes you look overly sensitive. Certainly no T. They are entitled to their opinion. If they object directly to you in terms that are such that you need to T 'em up, do so. If they show you up by yelling "that was weak" so the whole crowd knows they think the call stunk, T 'em up. But they are entitled to discuss the quality of calls amongst themselves without fear of penalty. What rule have they violated?