Even "liberal" figures such as Lawrence Tribe have conceded that it would require a Constitutional Amendment to allow the federal government to disarm the American public--as it is an enumerated right for individuals to be armed.

I suspect SR realized that quotes of Sarah Brady probably wouldn't sway anyone--just as quotes from the NRA-ILA would carry much weight with SR. But quotes from the Brady Bunch are really about all that exists these days in support of SR's position--that means no legally valid opinions. There are not, and never were, any authoritative historical comments of that nature.
President Reagan summed it up nicely, "Some people go through their entire lives wondering if they made a difference, Marines don't have that problem!!!"