Thanks for the ideas, fellas! I also like the idea of dousing the scat with bacon grease, and now I have an excuse to go out and buy some bacon (as if I needed an excuse

. A humane trap is another option I'd consider, and a large bale of manure is a cheap strategy but since these aren't house dogs I'm not sure how much effect it'll have.
I don't think making friends with the dog is going to happen. One afternoon I found a little snowball of a puppy wandering around my garage. The only place it could have come from was this neighbor's house, so I coaxed it back up the drive and gave it a shove toward home. Next time I saw it, it was a full grown Great Pyrenees barking it's head off and growling like a wolf from inside the sheep pen they keep it in. I have no doubt they've encouraged that dog and all the others on their property to be vicious. Some here would argue that's not the dog's fault, and I would agree. But that wouldn't stop it from trying to rip my throat out if it ever got out of the pen. I would defend myself from such an attack, but only as a last resort would I use a firearm. That said, I have taking to slipping a 38 into my pocket when I walk up to get the mail. I probably should have been doing that all along owing to the two legged predators that have cropped up around here in the last few years, some undoubtedly involved with or interested in the neighbor's pot farm.
This neighbor has already demonstrated he doesn't care what I think or about my welfare, not just with the dogs but over so many other issues that should have been cooperative efforts that would have ended up making life better for all concerned. The attitude is he's doing what he wants, regardless of the consequences to those around him. As somebody here said, he's making his problems mine.
For example, not long after I moved in I found a Rhode Island Red chicken on the road down to the lake. It could only have come from the neighbor's house, as the next closest place was almost a mile up the road and the chicken had a broken leg. I wrapped it in a towel and took it home, then started calling around to see if any of my neighbors was missing a chicken. They were the first I tried and they denied missing any even though they had several Rhode Island Reds in their flock. The chicken gradually recovered and figured out how to get around on it's bum leg, but when I found out it was a rooster I gave it to another neighbor.
In another instance, after hearing the local fire chief tell me he wouldn't send a crew down my driveway to fight a fire because it was too overgrown with brush and overhanging trees, I brought a bulldozer in to clear the hazard. This neighbor had told me on several occasions he was planning to clear the easement himself, but after two years had yet to so much as rake a single leaf. The easement is 60' wide, and I had it all taken down to bare dirt, leaving the larger oaks and pines in place, and pushing the debris into bus sized burn piles. My intention was to plant a barley/rye/clover erosion control mix when the rains started the following fall. I told the neighbor in advance that the work was planned, and he responded that what I had in mind sounded fine with him, and his son would get back to me if there were any questions or concerns. A week later I'd heard nothing and the dozer was on site. We had half the easement cleared out when he came marching down the driveway demanding that the work stop and threatening a law suit for damaging his property. I told him to check his deed to see that the work area was within the dimensions recorded there, but he still wasn't satisfied and insisted I "restore" the ground immediately with hay and push the burn piles onto my property. According to him the piles were an eyesore and would give the wrong impression to the guests that were coming to one of the son's wedding that summer. I asked him if they were more of an eyesore than the 40' green and red shipping container parked next to his gate and got nothing but a stare as a response. In an effort to placate him, I did as requested, spending about another $1K to do so.
Later that month I replaced the rusted and bent farm gate at the street with a motorized gate I fabricated, and his kid started hassling me about violating the easement dimensions again. I was shoveling concrete into post holes at the time and lost my temper. I told him that he needed to start minding his own business, because evidently that was the only way we were ever going to get along. I moved some stucco faux pillars up from the lower part of the property and the finished gate looks and works great. Two years later the neighbor started growing dope and figures he needs a motorized gate, too. He installs something more appropriate to a prison yard and piles up his old gate and posts against the back side of the pillars I'd installed. They haven't yet, but with all the problems we're having in the neighborhood lately I wouldn't be surprised if someone stole them. This is just the tip of the iceberg, and I could go on and on recounting his stunts and those of his family. But the point is, the guy's an @$$hat, and he's taught his sons and dogs to be @$$hats, too. No amount of kindness, talking, or threatening is going to change that. My sense is that the county needs to deal with him, and unfortunately it falls to me to get them to do their job.