Found the full story rather than a excerpt. Love the false info on the M16 as well.

But Menino expressed deep reservations yesterday about the plans. He said he had not been briefed on the proposal until a few days ago, and in comments to reporters he was clearly unhappy about the idea of officers patrolling the city’s neighborhoods with high-powered semiautomatic assault weapons.

(emphasis added by me)

The M16 is not high powered it is lower powered! Assault rifles were initially produced as lighter low powered rifles for Paratroopers to use as part of the mission of being a highly mobile unit. The Nato 5.56x45 round is the equivalent to American .223 caliber cartridge hardly what one would call high powered.