Why? Hitler stripped some people of their rights, including firearm ownership specifically to, to put it lightly, abuse those folks. Pro gun folks see the second amendment as applying to EVERYONE for that very reason.
You are correct to point out that Hitler didn't institute gun control across the board and actually reduced restrictions on 'real' Germans and that is noteworthy. But, that certainly doesn't make it OK to do what he did to the Jews, does it??? Them not being 'citizens' is pretty much Germany's 'Dred Scott' moment, isn't it?
Further, getting to the testimony, Hitler was never universally loved and cherished. He was feared, especially by Germany's conservatives, from pretty much day one. Strong Germany? Sure. But, more war? As we see in our lives every day, there is a strong impulse to go along to get along that can rather quickly become compulsory. This is, again, where basic rights come into play. Hitler reached his critical mass with the Reichstag laws and that was pretty much it.
I don't know how much history may have been changed if Jews retained the right to self defense, how much they would have actually resisted but, we do know what happens in the corollary.
The core issue remains; is the right to keep AND bear arms in this nation a right or a privilege? I would submit that what O'Malley and Bloomburg and Fienstein are after is it to be a government controlled privilege, period, and THAT serves the interests of the state and THAT is the core issue here.