First of all, any decent field will avoid mixing rentals and equipment owners. However seeing how business ain't doing that well around here some fields have little choice. These days I often carry a pump marker in my gear bag for when I show up and I get thrown in with the rentals. Before getting a pump marker I used to turn whichever marker I was using that day into semi mode and would not walk the trigger (I'd shoot with one finger.) It has gotten to the point where I also restrict myself when I'm amongst newbie equipment owners.
I'm privy to a fair amount of inside information from field owners, and yes douchebags hosing down rentals and newbies *are* killing paintball. I think Mike Phillips may be right about the adverse effects of high ROF in recball.
When I show up with a bunch of friends and we 'scare' the locals, it helps showing them you're not a complete asshole. Especially with kids, I take the time to talk gear, answer their questions. I let them try my markers. What we do also is that we split up: if me and my friends that day we're say 8 players, we split up 4-4 with the others. We now have two sets of jerseys (one green, one blue) for when we split up. When we see that one team wins 3-4 times in a row, we change some of the parameters of the game to let the other team stand a better chance at it.
Basically, it boils down to this: yes it is fun to get "kills" and win games. But if it comes at the expense of other players' enjoyment of the game, they'll start thinking paintball isn't that great for what it costs. And then you have nobody left to play with.