Leading article: We must hold fast to our values in the face of terror

The investigation into the attempted terror attack in Stockholm at the weekend is still in its early stages, but there are some tentative conclusions that can be drawn. The first is that the attack was incompetent. The car bomb had similarities with previous failed attempted attacks in New York, Glasgow and London. And the individual found dead in the area had been carrying an explosive device, which would seem to suggest that this was the bomber himself.

But the incompetence of the execution allows no complacency. Although just two people were hurt (other than the presumed bomber), this could easily have been lethal. Six years after the Madrid train bombings, the threat of terror still haunts Europe's streets.

An email sent before the attempted attack suggests that this attack was motivated by Sweden's military involvement in Afghanistan and the fact that a Swedish cartoonist, Lars Viks, in 2007 drew a picture of the Prophet Mohamed in a local newspaper that offended many Muslims.

The Mohamed cartoons affair, which began in 2006 in Denmark, continues to have repercussions. In January, a Somali man broke into the home of the Danish cartoonist Kurt Westergaard armed with a knife and an axe. In September an (unsuccessful) letter bomb was send to Jyllands-Posten, the Danish newspaper that published the original offending cartoons.

So how should democracies respond to this insidious threat, driven as much by religious offence as anger at Western military actions abroad? The answer is that we need to keep calm and defend our liberal values. The solution is not censorship of magazines or newspapers. In May an attempt was made to burn down Mr Viks's home. However offensive his art might be to some, he needs to be protected by the Swedish authorities. And the same is true of other Nordic cartoonists who now find their lives under threat.

Nor can censorship of ideas be any sort of solution. This is directly relevant to Britain since the Home Secretary, Theresa May, is considering banning Terry Jones, the American pastor who threatened to burn the Koran on the anniversary of the September 11 attacks, from entering Britain to address an English Defence League rally in February. Ms May has the power to exclude an individual from coming to the UK if they are not conducive to the public good – and she has been lobbied by anti-extremist groups to bar Mr Jones's entry. But the Home Secretary needs to think very hard before exercising this power. Unless it can be shown that Mr Jones will directly incite violence, it would be better not to make a martyr of him. The Obama administration made a mistake in giving Mr Jones's pathetic threatened Koran-burning stunt publicity by condemning it. A UK travel ban could compound this error.

Equally, the solution is not repressive domestic measures. The previous Labour government took a disastrous wrong turn when it responded to the September 11 attacks by detaining terror suspects without charge and curtailing freedom of speech through the religious hatred act.

The terror threat against the populations of Western states is real. But it needs to be treated like a criminal conspiracy, rather than an emergency that requires the suspension of our liberal traditions. Our police and intelligence services are adequately equipped to meet the threat. Our existing laws are capable of dealing with those who resort to violence to further their goals. And our societies are strong enough to withstand these challenges, providing we do not compromise our values.