There is no one size fits all answer to dealing with coaches. From your description, if I were your partner I would okay with your T.
As has been pointed out, your reported conversation with the coach was probably too long. However, at the 8th grade level many coaches are as ignorant as their players and a little (emphasis on the little) education can be a good thing. That's a feel you have to develop.
I will talk to a HC all night long as long as he's willing to keep the conversation appropriate. OTOH assistant coaches speak to me at my pleasure. If they address me in anything other than a respectful manner, well they pays their money and they takes their chances. And their ignorance of their true role and the boundaries that exist provides no shield for them.
However, unless the assistant's outburst is over the line, I will usually warn the HC that his assistant's behavior is about to cost him his box. A good coach will take care of it for me; the other kind will at least not be surprised to find themselves seat-belted (though they'll still complain bitterly about it).
Having said that, the occassional whack for the first offense is good for an assistant coach. It keeps him from developing a mentality that the first offense is a freebie because the official MUST give a warning. A little irrational fear is a good thing
