JuanCarlos makes a couple of good points. The incidents ARE often over reported in the media, making it appear more common than it really is (we gunowners can identify with that, I think), but the benefits of no knock warrants aren't worth the risk.
The only real issue is public safety, and whether the gains made by issuing no-knock warrants outweigh what danger they pose to law-abiding citizens. Which, at the end of the day, isn't much...you can find a long list of instances of dead law-abiding citizens, but those are over the course of a couple decades. Much like school shootings, statistically these incidents don't happen.
I'd still argue that the upside isn't worth it, but I don't necessarily expect people to automatically accept that.