That might be concerning if it were accurate, but it is not. Hitler relaxed the Weimar Republic gun laws while also restricting Jews from manufacturing guns or ammunition, and then banning them from owning any weapons. The rest of Germans were very much not disarmed.
And it is a quaint, outdated notion that a private citizen with a gun is going to stop an authoritative government.
Finally, the statement also presupposes that the only thing preventing a Hitler in the US are privately held guns. I find that view to be pretty dumb.