There are quite few dogs in the whites as it is very popular day hike destination and I expect that applies to many popular sections of the AT. Many of the northbound thruhiker dogs (who generally are quite well behaved by the time they get here) are already off the trail and every year a few end up having to go off trail or holed up in town for a few days due the very abrasive rock in the northern presidentials and the Mahoosucs. Folks swear up and down that their dogs pads are toughened up from hiking from GA but many dogs in general and on occasion thru hiker dogs end up wearing their pads off in a couple of days.
I find that hiking with poles really cuts down on dog issues. In general most dogs keep a bit of clearance when someone has poles. I wouldn't arbitrarily strike out at a dog unless the owner has no control and the dog is actively attacking but I have over the years have had to swing at a few that I suspect were not thru hiker dogs.