Of course it’s an argument because we can simply license based on predictors of burden. Small dogs which are projected to fall below a risk tolerance threshold should have less licensing burden.
Similarly, different classes of vehicles get different licensing requirements; saying all cars are the same is just lazy, and a regulation meant for big risky entities being applied to small ones is what we call regulation moats. We have enough pet owners that we should be able to quantify risks and burdens for the purpose of licensing. Here we have an article which provides empiricism on the community burden from cats.
I'm talking about whether anecdotes of safe dogs is an argument that we might need different levels of licensing. Yes it's an argument, especially in the face of empiricism on the community burden of cats.
It's as much about personality as physical threat.
Cats are far more skittish around people as a rule. There are practically zero stray/outdoor cats that will attack a person unless they're backed into a corner and provoked. The same thing isn't true for dogs, some dogs are simply aggressive.
It seems more likely that a free-roaming cat will get rabies than someones 6 lbs lap dog. Especially because cats (at least in my area) don't require licensing or rabies shots like dogs do.
Cats do too, maybe not as frequently, but I think the important factor is, that the damage is not as severe in most cases.
It probably is related to the size of the animals. If there would be more tiger-sized cats and more Chihuahua sized-dogs it would most likely be different.
I think "not as frequently" is a understatement. Cats are orders of magnitudes less dangerous to humans than dogs are, it's not even something I have to think about when I walk outside. Meanwhile, often times, the only thing that stops a dog from attacking me is the gate of their owner's house. Even that won't stop them from running at me and barking at me though. And yes, I've walked by a house with no gate before and two dogs just came after me and attacked my legs, one even biting me. I'm no dog hater or anything, in fact I like dogs, but dogs are only appreciable if they're on your side. I shudder at the thought that anyone would be able to get a pitbull and do whatever they please with it without licensing or repercussions for letting it loose on the neighborhood children.
EDIT: Forgot to say, it don't matter even one bit what size the dog is or how small it is. If they aren't on your side, they're capable and very willing to bark at and attack you.