Irate Coach - First time flagging a coach

[JugglingReferee]

As soon as this coach is yelling AT you in the way that you describe, and just 2 feet from you out onto the field, flag him, and get away from him. Let him sink himself if he wants to shower early.

The only thing I can suggest is that the learning point here is to recognize abhorrent behaviour and not to get worked up over it. Just flag it and move on.

As for issuing a sideline warning, I wouldn't have - i would have stayed with the USC. (But then again, since I work up here in Canada, our philosophies are likely different. It begins with coaches not being permitting on the field at all for any reason other than an injury.)