Last month, while ambling to work one morning, a young Indonesian in West Sumatra province was accosted, roughed up, and then taken into custody by the police.

His offence was that on his Facebook page he had queried the existence of God and thus committed blasphemy which, in Indonesia, carries a sentence of up to five years in jail.

Yes, it is 2012. And in Bangkok, Singapore and elsewhere, bookshops are full of works discussing the pros and cons of religious belief.

But in many other places a kind of pre-Galileo mindset prevails, where but to question any religious dogma is to court a modern-day Inquisition.

Secular Muslims in Indonesia, Brunei and Malaysia now find that laws of this nature are being enforced more frequently and more brutally.

Things are so bad that the International Crisis Group, a respected non-government organisation, has warned of a regional trend towards Islamic vigilantism.

In a January 26 briefing, the ICG noted the way gangs of Indonesian men increasingly use violence to enforce their interpretation of Islam.

The same is happening in many parts of Malaysia.

The ICG even claimed that Islamic vigilantes are becoming more like terrorists as the scope and complexity of their attacks grow and they move from sticks and stones to guns and bombs.

In its World Report 2012, Human Rights Watch, another international NGO, noted the same frightening trend and expressed shock over the impunity these gangs seem to enjoy in Indonesia.

All this would be bad enough if it were confined to the region’s Muslim-majority nations, but there are clear signs of heightened religious intolerance across the whole of Southeast Asia.

In Thailand, the antipathy of the Buddhist majority towards their Islamic compatriots was on shocking display last week when paramilitary rangers shot and killed four innocent Thai Muslims in the country’s south.

As commentator Kong Rithdee wrote in Saturday’s Bangkok Post: “It is amazing that this latest report of a glaring, everyday atrocity did not stir the anger of good citizens.”

But it did not. Indeed, nothing stirred except sanctimony and treacle.

For all Thais know that no real punishment will be meted out to the murderous rangers and that the brutal insurgency in the south will continue unabated.

A similar tragic scenario prevails in areas of Mindanao in the southern Philippines, where 700 American troops bolster Manila’s war of attrition against the local Muslim community’s bid for more autonomy.

As for Cambodia, Laos, Myanmar and Vietnam, there is a barely concealed animosity towards Muslims that runs across the entire society and is viewed as perfectly normal.

In Ho Chi Minh City, Tran Dao Anh, chairman and CEO of Diginet Technologies, told me that despite Vietnam’s current economic downturn, the country would recover and do well.

One of the reasons, Anh said, is because “it’s safe, there are no terrorists here – we have almost no Muslims”.

Days earlier, when I inquired at a Singapore Airlines desk in Changi Airport about flying to Cotabato City in Mindanao, the mature ultra-efficient lady was upset at not being able to help.

“Are you going to Cotabato on business?” she asked.

When I answered affirmatively, she cautioned: “It’s very dangerous, you know. They have a lot of Muslims there.”

In December, in the bar of Yangon’s Strand Hotel, a local journalist told me: “Muslims don’t belong in Myanmar. We don’t trust them.”

These and other remarks, often from otherwise intelligent and tolerant people, have become more and more common – and go some way towards explaining the rising tide of Islamic radicalism.

Certainly, one can understand even moderate and secular Muslims becoming angry and perhaps lending support to vigilante groups like Indonesia’s Front for the Defence of Islam.

That is the real horror: That in reaction to insidious and deep-rooted prejudice, moderate Muslims and non-Muslims alike become so alienated they begin to act like bigoted fascists.