Yeah, as long as they're:
1. waving a knife around threatening passerby and
2. advancing on the respondingn officers and
3. ignoring warnings in English and Spanish to "drop the knife...
Same goes for legally armed citizens. Seriously, if you're out shopping, say, and a crazy dude with a knife decides to take an interest in you, you're going to try to talk him down? Or use your Krav Maga knife takeaway technique you've practiced in the Dojo with a rubber knife? Really?
Dude, there’s no situation that the ancient secrets of the Krav Maga discipline can’t handle. Knife takeaway fails? Easy...you fall back on your other two moves, groin strikes and eye pokes.