[mikeash]

You never know, he might grab a gun and start shooting if you give him a chance.

Not saying it's right, but I think that's the reasoning.

[scott_karana]

And that's why all police officers are already armed with pistols.

A no-knock warrant with holstered pistols would be entirely reasonable in a residential, non-violent crime conviction, don't you think? (Well, I would debate the no-knock part :)