If you define "not difficult" as "any moron like you or me can/could do it", then no, perhaps it isn't. If you go by the real-world definition, though, "do most frigging morons seem to be able to do it?", then it must obviously be difficult as all Hell.

And never mind their fucking dogs -- although I'm still of the opinion that if I'm not allowed to shoot any dog whose owner doesn't scoop the poop, then the reason for that should only be because I ought to go after the party responsible and shoot the fucking owner in stead, but... -- Uh, where was I? Oh, yes: Never mind their fucking dogs, to see how impossible it apparantly is to impart some fucking manners, you only have to look to most people's children.

Which, all in all, leads me to side with Brenda and the Gryge: If those smaller breeds in practice don't get socialized (because their owners "regard them as toys in stead of pets" or for whatever fucking reason, it doesn't matter), then dogs of those breeds are in practice more likely to be vicious little arseholes. Arsehole is as arsehole does; if a mass murderer is still an arsehole even if he had a deprived childhood of broken handed-down toys, then a snapping biting little furball is still a vicious fucking beast even if it only got "Bella! Bella!" in stead of "Come here! Sit!" as a pup.