Investigating a noise:

[David Armstrong]

Of course there's a downside to this too. If people call without attempting to verify the noise is legitimate (neighbor taking out his trash for instance) then we tie up a lot of police resources on bad calls.

I don't think anyone is saying to do that. There is a lot of difference between verifying if a noise is legitimate and going out, or clearing a house. Nothing wrong with checking, lots wrong with checking to the extent you put yourself in danger needlessly. And I also don't think anyone is saying call the police every time you hear a noise.

The officer had let his guard down entering the back yard, expecting a cat, dog or some other simple explanation. Only this time it was a real intruder.

Not sure what that has to do with this. Officers get complacent all the time. Sometimes they pay a pretty heavy price for it.