It’s not the same as car insurance. With auto insurance you put other drivers and pedestrians at risk by driving on public roads. If you own a car but don’t register it and simply keep it in your garage, you don’t need it insured. So, if you’re going to walk around randomly spraying bullets, by all means, lets require insurance for that. Secondly, if the purpose of requiring insurance (stated or otherwise) is to make it prohibitedly expensive for someone to own a gun, then that in and of itself is infringing on ones right to own firearms.