Well, I should clarify that I was never looking to advance past the regional level. If you are fishing to pay your light bill and put shoes on your kids' feet, you better not feel one bit bad about front-ending your back seater.
Co-anglers know going in that they are fishing leftover water. So is every other co-angler in the event, and that's why there are two divisions --- pro and co. As soft as I was about sharing fruitful water, I did have to remind a couple of guys that they were not entitled to throw over my line or (much) past the center line of the boat. In fact, I came very close to bringing one back to the dock in a Central Pro Am event on Table Rock. First thing that morning, we were unable to run to my river fish because of fog. So the little twerp tells me he has a spot close by. We get there, I go to the front and drop the trolling motor, then I look thru the bushes (it was a flood year) and there is Dave Barker, who my guy had fished with the day before. I turned around and asked him, "Is this where you and Dave fished yesterday?" He says yep, like there was nothing wrong with taking me to Mr. Barker's spot. Fortunately, I didn't make a single cast and got out of there as quickly as I could . Aside from the ethical issue, it was strictly against CPA co-angler rules for him to reveal to me another boater's fishing spots or techniques.
Next, I had to take his hung over butt back to Ahoy's before he crapped his pants. By then, the fog was breaking and we were able to run up the river. For the first two hours, he continually threw in front of the boat, even over my line at times. Finally, after asking him repeated times to stop, I put him dead against the bank for an hour and when I tried treating him decent again at our next stop, he had miraculously learned some manners.