If you think about it, what he's saying is you can't give more rounds to the law abiding. The criminals aren't going to respect the magazine size limit, so his argument is complete nonsense.
He wants to criminalize anybody who carries more rounds than the police do, regardless of the intention of the person who "can outgun" the police. Very common "us vs. them" attitude.
Just another reason to not spend another minute in that hellhole.