Another vote for "delivery is everything". And kevinrideshorses, I think you were right on target. Sounds like you were respectful, considerate, direct without being harsh and considering what was happening , had a lot of self control!
I am open to advice, but also know my horses very well, so for me, timing of the advice is everything.
An example is this past year when loading my mare T after a club ride she refused to go in. Now I know she is blind on her right side and partially blind on her left, so I slid the divider over to give her more entry room. Then I lead her to the ramp, this time stopping her and letting her acclimate to the inside of the trailer. In she went. During all this, I received many words of advice and even someone trying to go behind her and "encourage" her with a crop. Lord grant me the patience!
So, I think your advice was timed well, and sounds like it was appreciated. He probably was thankful someone was able to take charge of this situation for him.