The award-winning Ethiopian journalist Eskinder Nega will turn 45 this month in Kaliti prison outside Addis Ababa whilst serving an 18-year sentence as a convicted terrorist. The government in Addis would have the world believe he is a reckless, even racist, agitator bent on violent revolution. Yet, a review of the evidence against him and his writings reveals a thoughtful and principled man whose only crime has been to urge, peacefully and publicly, Ethiopia's rulers to deliver on their long broken promise of peaceful, democratic reform.

"Democracy is so important to Ethiopia, because we need it to moderate the differences between civilization and civilization," Eskinder said in a 2010 interview. "I hope the EPRDF (the ruling party) will be pragmatic enough to realise reform would be the better option, even for itself," he added. "I believe in forgiving… that we shouldn't have any grudge against the EPRDF, despite what it has done. I believe that the best thing for the country is reconciliation. I believe in the South African experience, that model."

In February 2011, inspired by the Egyptian military's tolerance of pro-democracy protesters in Tahrir Square, Eskinder wrote an article urging Ethiopian soldiers to heed their example, should demonstrations break out in Addis Ababa. The column appeared on a US-based Ethiopian news website blocked inside his country. In response, the state security detained Eskinder, accusing him of inciting the public against the government. A senior police official threatened to kill him if he did not stop writing about the Arab Spring.

A few months later, after the government invoked a vague terrorist plot to imprison prominent journalists, lawyers, teachers, academics and other dissidents, Eskinder spoke out again: "None of the recent detainees under the terrorism charges remotely resemble the profile (of a terrorist). Debebe is probably the ultimate antithesis of the fanatic, his pragmatism, his easy nature, defines him," he wrote, referring to prominent actor Debebe Eshetu. "Neither do journalists Woubshet (Taye) and Reeyot (Alemu) and opposition politician Zerihun Gebre-Egzabher fit the profile. The same goes for the calm university professor, Bekele Gerba."

Just five days after writing those words, Eskinder was arrested again, and charged under the same terrorism charges. As evidence, the prosecution submitted a video of a town hall meeting of an opposition party where Eskinder expressed his opinion that if repression continued, the people's patience would run out and there could be Arab Spring protests in Ethiopia. The prosecution claimed that by making such statements he was using his constitutional right to freedom of expression as a cover to overthrow that very constitution.

Eskinder's treatment is emblematic of the conditions facing all Ethiopians and the systematic harassment and incarceration of independent voices. Journalism has its occupational hazards the world over, but in Ethiopia it is impossible to practice the profession honestly and with integrity. The country's anti-terrorism law is sweeping and harsh. It mandates a 20-year sentence for "whoever writes, edits, prints, publishes, publicises, disseminates" statements that the government deems support terrorism. Suspects can be held under these laws for up to four months without charge, let alone a trial – perversely reminiscent of the 90-day (and later 180-day) detention laws of South Africa under apartheid.

In fact, the anti-terrorism law of today's Ethiopia looks very much like the statutes the apartheid government enacted to suppress opposition and maintain a system declared a crime against humanity by the international community. Some of us remember vividly the Suppression of Communism Act of 1950 – later replaced by the Internal Security Amendment Act of 1976, under which even anti-communist writing was banned if it opposed apartheid, and writers were charged and convicted. Ethiopia's anti-terrorist statute is a close cousin of South Africa's Terrorism Act of 1967, which was just as all-encompassing; even the mildest opponents of apartheid became "terrorists" under this Act. Just as in South Africa, Ethiopia's anti-terrorism law has become an instrument of terror itself.

Many people and organisations around the world have spoken on behalf and in defence of Eskinder, but whenever these gross violations of human rights happen in Africa there is either muted protest or utter silence on the part of African writers, intellectuals, artists and media. Why should these violations be Bob Geldof's business and not ours? Surely we also care about human rights because we are directly affected, even more so than those based in the west.

For two decades, Eskinder has been an indomitable free thinker who has refused to give in to anger, resignation or exile despite persistent government intimidation. When his wife, Serkalem Fasil, accepted the PEN Freedom to Write award on his behalf she said that prison had become her husband's "home away from home". Serkalem, herself a fellow journalist and newspaper editor, was imprisoned for exercising her freedom of expression, and their son was born in prison.

Eskinder's continued arrest and the harassment of his family is a travesty that all freedom-loving Africans should protest against relentlessly. It is in this light that the African Commission on Human and Peoples' Rights should consider the complaint filed recently by Freedom Now and the Media Legal Defense Initiative on Eskinder's behalf.

What is happening in Ethiopia is a disgrace. An African like me, who is enjoying freedom in South Africa, should have long ago protested this case in the loudest of voices. My silence was complicity. It is important to curb the impunity with which some African governments act against the rights of their citizens. If Ethiopia can get away with it, so will your country next time, and you'll be the victim. It is first and foremost out of human decency that our voices should be heard. But it is also out of self-interest as prospective victims of repression. As the saying goes, if we are silent today, when they come for us there will be no one left to speak.