So you've already stated that it isn't reasonable to allow the other "arms". So why is anything more than a single shot barrel-loaded rifle allowed?
Of course the reason is that there is a massive industry in making guns and a rabid source of people that can be scared into buying their wares. The reason the laws are the way they are is because of the economics of the lobby and not any principle.
It's unreasonable to restrict ownership of arms unless you want to restrict violence to the government and organized criminals, which the founders most certainly did not intend.
Police killed more Americans in 2019 than mass shooters, how can you make an argument in favor of the cops and courts controlling weaponry? Did you miss the police brutality protests last summer?
I also don't understand how citizens of the US are meant to protect themselves against police with the weapons they're free to carry. Is the idea that US citizens are going to use their weapons to resist the police from arresting them? Isn't that just going to cause no end of bloodshed?
The vast majority of these incidents happen to hardened criminals that almost no one in their right mind would support. A small fraction of these incidents involve innocent people, or people involved in situations where violence is not the answer and de-escalation would have been a better outcome.
The police have a large amount of support because the people involved in these incidents are, generally speaking, bad people that the majority would prefer to be in prison. Most people don't think the police are an oppressive force that should be fought against with lethal violence.