So how do you explain the current government tyranny? According to you there should be none.
Seatbelts protect people from crashes, but they don't make you invincible.
An armed populace can, if the provocation is severe enough, form an insurgent movement and wage asymmetric war against an invading force. It's quite effective; we saw just how so in Iraq and Afghanistan. We were unable to make real progress until we finally developed a counterinsurgency doctrine that was based on getting the locals on our side. A more brutal approach would not have worked, as the Soviets discovered in Afghanistan earlier.
Firearms have historically protected against many local tyrannies. Even without proper firearms, Native Americans fought us to a draw, and had they been a more unified people, the face of the US might be quite different.
After the civil war, the confederates couldn't fight a conventional war, so they formed the KKK and used lynchings and such to terrorize newly freed blacks. The freemen defended their lands with firearms, and the Democrats working with the KKK pushed for some of the earliest gun control measures.
Tyranny doesn't, of course, come just from governments. The worst tyranny in the US is from criminal gangs terrorizing poor urban areas; those areas invariably have strict gun control.
Firearms are nothing without human spirit resolved to use them if need be. That's why the worst abuses of government power are, invariably, the popular ones. The war on drugs has been incredibly popular in the name of The Children, and it's still a minority view to oppose it.
And that makes gun control the greatest potential tyranny because so many people are entirely willing to give the police license to forcibly disarm their neighbors.