And if it's their lawn, don't they have a right to their own feelings?
a) They could hate dogs. OK, not a pleasant attitude to have, but you know what, it's THEIR LAWN. They don't need to justify hating dogs and therefore not wanting dogs on their lawn.
We are talking about a dogwalker who thinks he/she is entitled to control what another homeowner does/wants on said homeowner's own property because their (?deterrent?) vegetal clippings are an inconvenience or a minor potential boo-boo to themselves or their dog.
b) Maybe they have--or someone in their family has--a serious dog allergy. Even "hypoallergenic" breeds can cause allergies in some people...the likelihood of avoiding a reaction or having a serious reaction to dogs wandering lawns may be low, but they don't have to like it either.
Right, it cannot be expected that dogwalkers can prevent all "accidents" on someone else's lawn...therefore perhaps use your leash, and training, to keep them off lawns where you know they are unwelcome??
Dogs do not have to "understand property lines", they just need to be able to heed their owners' commands. And don't tell me they can't be taught to keep on sidewalks. Otherwise, seeing-eye dogs would not be possible.
This isn't about whether YOU are someone who picks up your dog's poop. 49/50 dogwalkers might do so, but it's the 1/50 who doesn't that can make people not want to see dogs wandering on their lawn.
I absolutely love dogs, but many dog owners are sloppy, irresponsible jerks and I don't trust randoms to be conscientious. I have come into my driveway to see some dogwalkers acting like my property is theirs. I'm not even glaring, just standing there looking without a smile on my face for them to *slowly* get the clue that I don't like them letting their dog play on my lawn and then they tug on the leash.
My mom loves dogs so she plasters walls with calendar photos of dogs, computer screensaver is a dog...but as soon as stranger dog and stranger dogwalker is on her lawn, she doesn't like it, either.
I'm not OCD about it so you don't need to speculate on my, nor someone's psychological state. Just stick to the facts -- if you know your dog is not welcome on someone else's property -- keep dog off -- their property is theirs.