They could nock, they could die, they could loose evidence. No knock warrants for high risk arrests are a good idea. We don't know what the informant said, he's telling two stories (as they tend to do). I'm assuming that these police were all wearing clothing identifying themselves as such. If you shoot at them because you're afraid of dying that's exactly what will happen to you.
Such is the price of a free society. I don't think highly of arguments for safety or the need to find evidence in order to flaunt the constitution.

Don, I don't think Doc_bean was trying to equate you in any way with Nazi apologist, he was just pointing out that the cops can't get off the hook just because they were ordered to do this.

Crazed Rabbit