I don't really understand why this is controversial. The sanctity of the home must be protected, but that's why there's a warrant process. But in case I had any doubt, Justice Breyer reminded us why we need more Alitos and Robertses on the court:
It weakens, perhaps destroys, much of the practical value of the Constitution's knock-and-announce protection.
The Constitution has a "knock-and-announce protection?" That must be in the Eleventeenth Amendment.
The only "practical value" I can see in the old rule is the value to the criminal who has extra time to hide or destroy evidence, or even escape. Once the warrant is issued, due process has been upheld. The ONLY benefit to requiring an announcement is to the criminal flushing drugs down the toilet.
UPDATE: Here's the opinion itself (PDF). And I was wrong initially, as I should have suspected I would be when relying on the Seattle Times for legal analysis. The knock-and-announce rule is still in effect, but the exclusionary rule is not applicable to it under these circumstances.
Check out the facts behind the arrest in particular. The door was unlocked, not broken down. There were large quantities of drugs and firearms, including a loaded gun hidden in the cushions of the chair in which the suspect was sitting. I just can't see how this is unreasonable.