So I guess this counts as a really big oops.

Seventeen people dead, 122 injured in a bombing last Saturday in a residential neighborhood in Riyadh, Saudi Arabia. The attack is said to be the all-too familiar handiwork of al-Qaida. However, most of the people hurt and killed were not Americans, as apparently was intended, but Arabs.

A suspect being held by Saudi officials has reportedly told them the terror network believed the compound was rented by the FBI. Turns out it wasn’t. Turns out al-Qaida made a mistake, for which many of its fellow Arabs paid in blood. And flesh. And bone.

I’m guessing “Sorry about that” wouldn’t quite cover it. Ditto: “My bad.”

Not that any of us should hold our breath expecting the Osama bin Laden gang to express anything as human as remorse. Still, the terror ought to be instructive, if not to al-Qaida, then to its lingering apologists.

“One man’s terrorist is another man’s freedom fighter.” How many times was that axiom tossed about as crews were still clearing the rubble from the World Trade Center site? It was a facile formulation made all the more problematic by the fact that it contained a kernel of truth. Certainly, the British army thought none too fondly of the guerrilla tactics Francis Marion, the “Swamp Fox,” used against it during the Revolutionary War. Nor would the white South have sung hosannas to the insurrectionist John Brown, who seized a federal armory in the days just prior to the Civil War.

It requires no great leap of imagination to see how some might have branded both men terrorists. And never mind that they fought for causes that have since been vindicated a hundred times over.

But it’s disingenuous to suggest that al-Qaida is simply a Muslim John Brown or Francis Marion. Granted, a cause might be subjective: One that seems controversial now may seem heroic in 50 years. Tactics are another matter. Al-Qaida strikes civilian targets purposely, calculatedly and indiscriminately. It’s hard to conceive of the cause that would make that OK.

This isn’t the first time these supposed defenders of Muslim grievance have hurt their own people. If nothing else, it’s a virtual certainty that some of those killed in the Sept. 11 attacks were Muslims; the victims hailed from dozens of countries, including such Muslim strongholds as Pakistan and Iran.

Nor should that come as a surprise. Extremists often justify the murder of innocents as a necessary evil in service to a greater good. In al-Qaida’s case, that would mean its hope to drive the Saudi royal family from power and the American military from Saudi Arabia, location of Mecca, Islam’s holiest place.

So it blows things up, the end apparently justifying the means. And many in the Arab world — the so-called “Arab Street” — seem content to watch with silence, if not applause. But the Riyadh bombing has provoked a sterner response. An Egyptian columnist condemned it as the work of “criminal terrorist groups.” A Saudi editorialist said al-Qaida had perpetrated “horror.” Even al-Jazeera said on its Web site that the choice of targets “may seem counterproductive.”

It’s not much, but one hopes it means those Arabs who need to are finally waking up to the fact that people who bomb houses and cars do not defend Islam.

I guess it’s easy to be seduced by violence when those who carry it out claim to be on your side. It is easy to mouth pieties about the carnage, then turn away and enclose yourself in your own righteousness. It is easy to say “by any means necessary.”

Saturday’s atrocity is a harsh reminder that doing such things invariably comes at a price. And perhaps paying that price leaves the Arab world a little better equipped to understand what should have been obvious a long time ago.

Al-Qaida is not on anyone’s side.

Leonard Pitts Jr. is a columnist for the Miami Herald.