What merits an USC on the coach?

[wisref2]

Here's my approach:

If it's personal - he's very likely to get a flag, especially if anyone else can hear it. The second comment he made to you would have drawn a flag. The first one would have at least earned a friendly, but very stern warning.

If he questions your integrity, you have to flag it. (calling you a homer, telling his players that they won't get any calls because your crew is terrible, etc.)

If he's out on the field and complaining, flag it. How far on the field? The 9-yard marks are certainly too far, or outside the 25 yard line of the team box.

Swearing when someone else can hear it is automatic. Swearing when nobody else hears it is borderline - you have to consider the situation and what has happened before. Error on the side of tossing the flag.

If he's playing to the crowd or inciting the crowd or his players, flag it.

And then sometimes, it's just not worth throwing the flag. It's kind of like art - you'll know it when you see it.