I had to put up with that sort of stuff in my old neighborhood. If someone found dog poop in their yard than it automatically meant the first person with a dog that they saw was responsible. The first time my Buttons was just a pup. After walking the same path for a couple weeks, I took a different route. I go up one street and Buttons starts sniffing a fence pole. Suddenly this guy slams on his brakes, leaves his car in the middle of the road and comes over to *itch me out about dog poop in his yard. Explaining to him that this was the first time I came that way didn't matter. At one point I though we were going to fight. Even though the guy was twice my size I was more worried about Button's getting hurt, so I tried to make sure it didn't come to blows.
Another time some woman *itches me out because we walked past her yard. I know for a fact we didn't leave anything in her yard. And yet in the coming days I see her daughter take their dog for a walk and poop on other peoples yards. The last time Buttons & Bows were off leash as we headed to a field we played in. At one point I turned around and didn't see Buttons, so I ran back toward the corner we came out from. Just as I got there, she walks around. I noticed that there was some guy watching us from his porch. The next day a big ugly guy comes over and *itches me out. The guy on the porch was his cousin who told him Buttons pooped on his lawn. Well, he knew that I didn't see it happen, he should have said something. This guy was nuts too, made all kinds of threats. I tend to not back down with blow hards, but I also let them rant at me without responding in kind. Probably best that way. I'm certainly glad I don't live in that redneck area anymore.