In August 2,000 men, women and children, members of the 64 indigenous communities living in the Isiboro Sécure National Park, in eastern Bolivia, set out for La Paz. Their aim was to present to President Evo Morales their protest at the proposed 400km highway that would cut through their territory, an area of extraordinary environmental importance. Forty days later, they were attacked by police, teargassed and beaten at Yucumo.

On the following day, the Bolivian government minister Sacha Llorenti appeared before TV cameras to defend the brutal police assault. Shortly afterwards, Llorenti resigned, while Morales himself then issued an abject apology, claiming that he had not ordered the attack and suspended the road-building programme. Others said that he was responsible; as president he is also commander of both the armed forces and the national police. Defence minister Cecilia Chacon had already resigned in protest, claiming that this was not what the government of president Evo Morales was elected for.

Evo Morales was the beneficiary of a wave of mass popular protests that began with the "water war" in Cochabamba in 2000 and was followed by similar mobilisations over water and more generally over control of the nation's oil and gas wealth. At the heart of the movement was the long struggle of the country's indigenous populations – more than 50% of the population – for social justice and the recognition of their communal rights. For them, Morales's election to the presidency in 2006 was a collective victory.

When the powerful, predominantly white, state leaderships of Bolivia's eastern provinces tried to break away from the rest of the country in 2008, the resistance mounted by the local indigenous populations in co-ordination with their allies in the high mountains of the west, effectively saved Morales's government. And the constitution of 2009 seemed to justify their confidence. It established the "plurinational state of Bolivia" and contained an explicit defence of the communal rights of the Indian communities over their traditional lands – though their own term was "territory" because it embraced not only the physical land but their cultures and traditions too.

Having nationalised gas and oil and introduced some immediate measures of social welfare, it seemed that the government of Morales would indeed, as he movingly declared at the Copenhagen Climate Conference, give priority to the protection of "Pachamama" (Mother Earth) and the long neglected rights of Bolivia's first nations. The march from the national park – or to give it its full name the Indigenous Territory of the Isiboro Sécure National Park (Tipnis) – was intended to insist on those constitutional rights.

The marchers and their organisations were arguing that the chosen route of the new highway would cause maximum environmental damage and disrupt and eventually destroy the local communities – and that its real purpose was to give easy access to multinational oil and gas companies. Morales angrily denied this, denouncing the marchers as manipulated by foreign interests. He has used the charge on previous occasions – in December 2010, for example, when his powerful vice-president, Alvaro Garcia Linera, announced an 83% rise in petrol prices and backed down only when mass protests brought the country to a standstill.

The attack on the Tipnis marchers will serve only to fuel a growing disillusionment. The guarantee of prior consultation in the constitution was ignored over petrol price rises, and again over road-building projects like this one. And the defence of Mother Earth rings hollow when it is clear that the economic strategy the Morales government has adopted seems to rely on new contracts with a range of multinational companies to develop oil, gas, lithium and uranium reserves – in other words, the very extractive industries that had gutted Bolivia's subsoil at the expense of a population 69% of whom were living in poverty when Morales came to power.

Morales has argued that the integration of a hitherto fragmented country was his first priority – and he has justified the Villa Tunari-San Ignacio de Moxos highway through Tipnis as part of that process. Yet it was originally conceived as part of an IMF-designated "transoceanic corridor" which would open the Amazon regions to global trade – and in particular to Brazilian multinationals like Petrobras, which is aggressively present throughout the region.

When Morales described the marchers as tourists he was ignoring an uncomfortable fact; that they were marching to defend a model of development that could offer an alternative to a destructive global capitalism, a model based on collective aspirations and respect for the natural world and the human beings who shared it. It was his own words they were bringing back to him, before they were stopped at Yucumo.