One plus to the people who are running their generators all day is that you know they have a generator and plan on using it, so you can stay well away from them. We rarely camp in campgrounds, but if we do, and there is an option we camp as far away from those with generators as we can.
The worst thing is when have a nice isolated dispersed camping spot, and someone pulls up within earshot and fires up their generator. As folks who enjoy the beauty, natural sounds and silence of the great outdoors, we can make a conscious choice to avoid camping near others with generators, ATVs, boomboxes etc. However there is not much we can do to stop them camping near us.
I am sure there are a lot of folks who will claim it is a free country and it is crowded out there, both of which are true. But you are also free to break wind in an elevator and loudly discuss your sex life on an airplane, but the expectation is that you don't out of courtesy to those around you. The other argument I often hear is that I have a Honda and you can barely hear it. For many of us, being out in the wilds is getting away from the constant 60Hz hum of civilization so even your barely audible generator can still be annoying.
I understand that it is crowded out there and you sometimes have to camp closer to your neighbors than you normally would - but if you do respect your neighbors experience.