It's really amazing the way most of the big dogs put up with all sorts of various aggravations from little dogs. My Bear would let little ones we ran across on our walks get by with murder, snarling, growling, barking, even nipping his ankles, when he never tolerated a dog near his own size or larger so much as snapping. An aggressive move from another dog always got an instantaneous pin with Bear holding it down by the neck and growling until the dog would lay still. He never hurt another dog; he never was the aggressor; he just didn't put up with disrespect.
The little ones, though . . . he just looked at them like they were from another planet and went on. My three now are the same way. There's a miniature Schnauzer in the trailer park that they let out every now and then and he'll invariable come up our driveway looking for trouble, growling, barking, lunging at Bimmer and the girls. They just ignore him and step over him. Once in awhile they'll stop and put their faces down to examine him. For some reason that seems to make him homesick, lol!
There used to be a Jack Russell over there (they moved away) who loved to go hunting in the woods with Bimmer. It was such a 'movie moment' to see the two of them meet in the lower pasture, then trot into the woods together, noses to the ground, tails waving in the air - Bimmer's huge plume and the Jack's funny little stub tail. Bimmer's got a funny little hop he does when he's in high spirits and the Jack even started doing that too.