I had a similar situation at the F-18 Canadian Nationals where I was the PRO.

After the racing, I was approached by one of the Quebec teams and asked if I was going to DNF the two or three boats (out of 37) that didn't make the weather offset mark in one race. I replied, "No, I can't (citing rule A5), but you are welcome to protest them if you wish." They said, "No - you must protest them! We don't want to make enemies!"

I said, "We didn't witness it from the signal boat, but my weather mark boat operator could be a witness for you in the hearing." They still didn't want to protest.

I already knew about it - because the weather mark boat reported it when it happened and was keeping track of sail numbers. They were all back-of-the-pack sailors who were having a bad day.

Personally, I'm against the RC protesting competitors, unless I personally witness an egregious foul and/or a question of sportsmanship.

However, my MBO's are meticulous note takers and will be happy (well maybe not happy; you're cutting into their beer-drinking time by requesting their presence in the room) to be your witness when you (as a competitor) file your protest.