But once settled in the northern city, the telecomms graduate found himself driven by another cause: protecting migrant workers from ruthless exploitation in the farm fields of the country's south, often at the hands of organised crime.
Now 31, Sagnet is soon to be named a Knight of Italy's Order of Merit in recognition of his work in exposing what many have described as a modern form of slavery.
"People talk about poverty and misery in Africa but, here, in southern Italy, in the heart of Europe, I have seen human beings stripped of every last scrap of dignity," the activist and writer told AFP in an interview.
Sagnet first arrived in Turin a decade ago. It was only by chance that, in 2011, he discovered "caporalato", a notoriously exploitative system under which farm owners recruit fruit pickers and other seasonal workers through an intermediary.
A failed exam meant the student was no longer entitled to a maintenance grant.
"I had to make some money and so, on the advice of a friend, I went off to pick some tomatoes," he recalled.
His trip saw him end up in Nardo, on the heel of the Italian boot, where he had heard a farm was looking for day workers.
- 16-hour days -
"At the place there was a tented village with 800 workers living with only five showers and unimaginable hygiene conditions," he said.
"There were Tunisians, without doubt the biggest group, but also Moroccans, Angolans, people from Burkina Faso, Mali... I was the only Cameroonian."
Under caporalato arrangements, now outlawed but still widespread, the employers, who are the real beneficiaries of workers' labour, avoid both payroll taxes and responsibility for the workers being paid illegally low wages.
The intermediaries, meanwhile, can claim to be paying them correctly while making deductions for services, ranging from transporting them to farms to providing bottles of water while they toil under the broiling sun of the Italian south.
The involvement of criminal gangs in the system means Sagnet's efforts on behalf of his fellow Africans mean his life remains under threat.
In a 2015 report, Italian trade unions estimated the number of mainly African workers labouring under caporalato conditions at between 300,000 and 400,000.
Sagnet's experience of the system involved spending a week waiting for work before he met one of the gangmasters who oil the wheels of the illicit scheme.
His identity card was soon confiscated -- he later understood that, as a legal resident of Italy, his paperwork was valuable for facilitating the recruitment of other, clandestine, workers.
Despite the heat, 16-hour days were not unknown, for wages of 20-25 euros per day ($21-$27), from which the price of water and sandwiches would be deducted.
"Some people worked through Ramadan, when they could not eat or drink (during daylight hours)," Sagnet recalled. "If someone fainted, they would not be helped up, anyone who asked to be taken to hospital would have to pay their transport."
- 'Supermarkets to blame' -
When, one July morning, the owner of the farm announced an increase in workloads without any increase in pay, Sagnet persuaded his fellow workers to down tools.
"We blocked the road, traffic jams built up and the police arrived, local media too.
"It was what we wanted, to attract attention to the conditions we were working under."
Without seeking the limelight, Sagnet became the spokesman of the mini-revolt, for a strike that was to last a month and end with the workers winning improved pay and convictions for several intermediaries and employers.
Other arrests followed in other regions and a law criminalising caporalato arrangements was adopted by parliament by the end of the same year.
Sagnet returned to his studies but has not given up the fight. He worked for a time for one of Italy's main union groups, and last year saw him publish "Ghetto Italia", a book in which he blames major retailers for the conditions in the farms that supply them.
"In their drive for profit they force producers to always be looking to cut their costs, something they can only do on the backs of their workers, by paying them less," he said.