These types of guys have been around a long time. I can remember fishing with my dad and it was a yearly occurrence to have someone cut us off like that, which led to several confrontations. My Pop was never one to not call someone on their arrogance and stupidity, so he would usually fire up the big motor and cut right in front of them. One time an old boy grabbed a tire iron out of his rod box and trolled over to us until my dad told him to never brandish a weapon that could be taken away and used on him. He backed off and finally left. I don't even get within 500 yards of someone when i see them on a spot, and sure as hell don't get in front of the bank they are fishing.
But it happened to my son and I fishing a derby Saturday, dudes come rolling in about 40 yards in front of us in the back of a cut, drop the troller, and start chucking A-rigs at docks in 15 FOW. I just laughed and told my son lets go, there are hundreds of banks that fish the same way on this lake. So on to the next spot we go which ended up being a blessing, because we got on a pretty good bite.
I hear you Bill on the green lawns that are springing up at all these folks houses on the lake. That goo is really nasty back in Wolf Pen and Little Wolf Pen hollow, the entire back end is loaded with it. Nitrogen rich run off and septic tank leaching is never good on a lake.