If you meant "no-knock" literally: I don't know if a no-knock raid is such a horrible thing if there is a legitimate warrant and the evidence is readily flushable, or some other reason (e.g., violent armed criminals are preferably taken at 2:00 AM while they sleep in a no-knock raid) is OK'd by the judge issuing the warrant.
The important essence of the 4th Amendment is that a member of the judiciary approves the warrant, not that warning (knocks) is given before entering. That said, no-knocks do have the danger of scaring even law-abiding citizens into lethal defense attempts, and so judges should not be pushovers when it comes to issuing them.
The ammendment is supposed to protect the rights of the people, not to the rights of the government. Judiciary approval is an important element of the fourth ammendment. However, more important is the first part of the ammendment that offers the purpose of the ammendment itself - that is "the right of the people to be secure in the persons, houses, papers, and effects..."
The practice of "no-knock" raids places in grave peril this right and the people subject to its abuse. The sad fact of the matter is that the police have used this tactic irresponsibly, even to the extent to where they have inflicted death and injury upon innocent and hapless people who have committed no crimes. In some cases this is because the police do not even have the right address. In other cases it is the actions of overzealous drug agents that turn lethal (e.g., the 11 year-old shot in the back and killed in botched drug raid in Modesto, CA in Sept. 2000 - no drugs found in the house, btw). This, apparently, is the price we pay for inane and poorly thought-out policies like "zero-tolerance." Even guilty people do not deserve to be shot and killed for such crimes as possession of drugs. If the government wants to kill people for capital offenses, they should make the effort to conduct a trial, convict and sentence defendants according to the law.
You apparently think the no-knock practice is acceptable because it prevents people from flushing their stash. I argue that if someone has so little contraband that they can literally flush it down the toilet to avoid detection, then it is not worth the effort of the cops to conduct the raid in the first place. I think the rationale the judge in the above article uses to dismiss the "smell test" supports this view.
The list of victims of "no-knock" raids is getting longer by the day. These deaths are the ultimate infringement of rights that the fourth ammendment is supposed to protect. Law enforcement needs to come up with better and safer methods of executing searches and warrants for arrests (like in Waco, they could have picked up Koresh when he was in town - but the BATF had to "show its muscle", or like how pointing guns at Elian Gonzales' family on Easter morning could and should have been avoided). The paramilitarization of our police forces is not indicative of a free society.
How about returning to the old-fashioned way of having cops just knock on the door and announce themselves and their intent? "Open up, it's the police...we have a warrant..." -- remember Joe Friday on Dragnet, or Pete and Jim on Adam 12? Why not serve people with search and arrest warrants as they enter or exit the premises? Is it not a crime for people to fail to comply with legal searches? Let judges and juries know, when and if a case goes to trial, that the defendant was uncooperative with respect to the issue of the warrant (this implies guilt as does flight). How about any alternative to the reliance upon and escalation of violence on the part of the government?
Save the no-knock type raids for the Islamist terrorists and other suspects known to be violent and worthy of the lethal force paramilitary assualt tactics represent.