Maybe he either doesn't explain procedure well or teaches by example or has dealt with other "invited crew for the day" before that couldn't comprehend what he was trying to explain or maybe he was annoyed that you were on the boat after your rigging error. Unless you have been in his shoes you really don't know his motivations.
For example...I was told that a "catsailor" wanted to crew on my boat. Experience level was around 5 years sailing a H16. I thought this person would understand how to trim a jib, weight transfer, where the downhaul and luff tension were approximately. What I didn't expect was a supposed "sailor" that wasn't familiar with the term "clew". So here we are on a medium air day and my asking if this person is certain about going out. The answer was lets go... After twenty minutes it was time to go because of a forgetten appointment. When I beached this "crew" was off the boat offering no help about placing the boat into the wind and up the beach pucking their guts out in front of several people. "I will never do anything like that again!" was the last thing heard.
The point is that the "new crew guy" has to prove himself worthy of being on board! No one knows the new crew's abilities! Especially in a race scenario where team work is developed over sailing/racing experiences over time not one afternoon. He may have had experiences where a "new crew" had caused problems.
You might inquire how many times a "new crew members" have been dropped into/onto the regular crew???
AT the 2001 Corsair Nationals I was booted off two crew lists because I had no experience as a spin crew on an F31R. The third F31R guy was high centered and I pitched in to push him off. Every crew on board had experience with the spin but me but I got to go. After two days training this F31R crew [5 sailors who had never seen each other before] competed to 10th overall . After watching for a couple of hours I started doing what anyone didn't want to do. From going to the low side to retreive a spin sheet dragging to hoisting the main with a broken sheave in the mast. By the first race we had designated specific duties to each crew as well as taught me by example how the "best method" each duty was to be performed.
I have been racing since 1959 and have learned one lesson... theres my way and the skippers way. I really don't care what knot is used or how the sails are trimmed unless I'm the Captain and then I do care and expect it to be done as I want from previous training/racing experiences. The new guy has to fit even if his feelings are bent...Actually I expect the new guy to be in the grease as soon as we leave shore.
thom
pics of the races can be seen in the photo section at :
http://home.att.net/~t.r.merrill/wsb/html/view.cgi-home.html-.html