The actual article linked (NYT) covers it all in much greater detail, the gist of which is: one-size-fits-all mandatory sentencing sucks, doesn't allow for the judge to take into account other factors, and largely affects people who aren't in the process of committing a crime. I'm no Brady sympathizer, but both sides are hell-bent on putting their thumb on gun crime - and pass some absolute stupid laws in the process.
My personal opinion is that the people that this "crackdown" targeted was not the demographic that the Brady campaign expected, and they are lightly pushing back accordingly. Especially considering that so many people that support them also support justice reform, etc.