I agree, some do ruin it for others. This is the case with almost every hobby. This is a huge gripe of mine, so please bare with me while I rant.
I fish some as well - and do some liesure boating with family. I can tell you this - the percentage of assholes that are fishing is about the same as the percentage of assholes on PWC - the thing is there are a lot more people fishing.
I've gotten flagged and yelled at numerous times - and Im (IMO) very polite on the water. A few times, I've had people who were fishing either IN or just outside the channel bitch at me for running IN the channel - WTF did they expect? Other boat traffic is just as likely to spook the fish. Where did they expect me to run?..outside the channel to avoid thier stupid asses roped to a channel marker? lol
I always go under bridges in the center span at low speeds (or idle when required). I've had weights thrown at me....well, now that my wife will be riding with me, if someone throws anything at her, Im going to park the ski and toss their hillbilly ass in the water.
I'm a nice guy, so I try to avoid people fishing/kayacking/surfing/swimming/all that... BUT what people don't realize is that each of these activities have an equal right to the water. Sometimes how one person excercises this right interferes with someone elses idea of a good time and thats a chance you have to take. Like I said, I avoid people doing their own thing, but if there is a guy who sat there waiting for a school of fish and a PWC screws it up for him (at least he says that it was the PWC fault - truth be told hasnt caught crap all day, right?

), he should realize that its a chance he takes when fishing in public areas.
Moral of this rant: Try to have fun without screwing up someone elses good time - and that goes both ways.
Done with rant