We think we saw your friends come in to Totonaka last night.
It's very unfortunate that this happened, and hopefully won't happen to them again.
Unfortunately, except for when the toll roads/highways/freeways are marked 110km, it is easy to speed. The speed limits are very low and no one drives at that speed. Leaving Hermosillo going south, the speed limit currently doesn't go over 80 because of the construction until you get fairly close to Guaymas, and most of it is 60.
North of Hermosillo the road is outstanding and it is very easy to exceed 110. In Hermosillo proper, the speed limit is 40 to 60.
We are all encouraged never to pay mordida. Tickets in Mexico are cheap. However, usually most of us are in a hurry, are hot and tired, and don't want to deal with going downtown to the police station to pay to get our drivers license back. We should probably get over it, that is the only way to stop this process. Just say, "Give me the ticket." Most of the time you will probably be sent on your way with an angry look.
Then of course is the language barrier. Yes, we have had similar incidents twice, both were set ups, and we made the wrong choice, we paid. We should have just asked for the ticket. In both cases we have no doubt that if we had asked for the ticket, we would have been sent on our way.
Does this make his "ticket" right? No. Is there anything that can be done about it? The margaritas were a good idea. Try to keep your sense of humor and continue with your vacation.