Not even under the acute threat of terrorist attack does the end justify the means.

Two of the four main players in the thwarted bomb attack against an airliner in Detroit were former Guantanamo inmates. One of Barack Obama’s major election campaign promises was his intention to close the prison camp. The latest event in Detroit has put that closure in serious doubt, and not only among Obama’s opponents. They maintain that the failed attack proves the absolute necessity of keeping it open.

But this argument confuses cause and effect. To send people to Guantanamo merely because they are suspected of criminal acts and to keep them locked up indefinitely with no recourse to trial brings nothing but shame to a country that claims to carry the banner of democracy and human rights throughout the world. Even in the presence of acute terrorist attack, the end never justifies the means; on the contrary, these means desecrate the purpose.

That’s the decisive argument against Guantanamo and this latest failed attack hasn’t changed that. On the contrary: it’s proof that rather than neutralizing terrorists, the prison actually creates more of them. U.S. intelligence personnel and others know that the very name Guantanamo is used by al-Qaeda as an effective tool to recruit new warriors against their archenemy. How could it be otherwise? For the Islamists, there’s no better proof of the West’s double standard than Guantanamo.

If Obama gives in now to the political pressure his opponents are subjecting him to, he might as well forget all previous and future gestures he may want to make toward the Islamic world. He will have surrendered the most powerful weapon in his arsenal: his credibility.