"You restrict our freedom"

YouTube link.

"Does something that would limit magazines that could carry 100 rounds, would that infringe on the constitutional right?" host Chris Wallace asked [Senator Ron] Johnson [R-Wisc] on "Fox News Sunday."

"I believe so," Johnson replied. "People will talk about unusually lethal weapons, that could be potentially a discussion you could have. But the fact of the matter is there are 30-round magazines that are just common all over the place. You simply can't keep these weapons out of the hands of sick, demented individuals who want to do harm. And when you try and do it, you restrict our freedom."

I come from a family that has used guns for hunting (pheasants and deer), so I'm not anti-gun per se.  But I frankly do not understand the mindset expressed here.  Perhaps some clear-headed, well-reasoning reader of this blog can offer an explanation.