A lot of ecosystem folks are complaining about nitrates. They complain about cow shit from cows that ate only natural pasture (whatever is growing). Essentially it is a "cows wouldn't naturally be here in such quantity, and the quantity is the pollution" argument. Because nitrates are totally natural things that nature totally knows how to deal with. But in large quantities they cause huge algae blooms (which humans don't liike) and change the ecosystem.
But to me this is a tiny thing of little concern. Far less concerning than the dumping of surfactants, which is less bad than the dumping of non biodegradable plastics, which is less bad than the dumping DDT, PCB, HCB, HBCD, etc, which is probably less bad than dumping radioactive waste. So it's at the bottom of the scale.
I would not worry about dog shit.