I think we'd all like to go over and have a polite word and if it turned sour hope we came out best, the problem arises if there is a few of them or said idiot gets on the phone to his mates to come on down, I think some fisheries are more bothered about getting money and will turn a blind eye to such things as they dont want the hassle, I once had some young lad come chat to me as I was doing well after about 10 minutes he just started fishing in my swim sat a mere 2 feet from me, then had the cheek to ask for bait!! I politely asked him to go back to where his parents were which he did, but he was such an annoying child and for those who have seen Bad Santa the absolute spit of the little fat lad in that! i dont mind the odd bit of asking what bait ur using etc as we've all done it but that just took the biscuit in my opinion. Having said that other times I've seen a few people and made that age old mistake of judging by looks which I will admit I was genuinely ashamed of as I dont think it fair to judge on how someone looks, my tattooist a prime example most people would look at him and rather cross the road than walk past him but his appearence is nothing like his personality, so in my rather drawn out way I would say if you think a quiet and polite word will do the trick go for it but it could potentially turn nasty if they are of a low mentality