The noisy blue-light convoys and the private jets ferrying African leaders to and from Harare, Zimbabwe, over the past month have now departed.

They came, they sang the praises of the country's late former president, Robert Mugabe, and they have now left the Zimbabwe of food and fuel shortages behind.

Like the memorial service and the very quiet funeral afterwards, the debates about Mugabe's legacy are fading into the past.

What we cannot ignore, however, are the troubling questions that we Africans must answer urgently, given the effusive tributes to Mugabe by some of our political leaders. The most urgent of those questions is this: do African lives really matter to us Africans and our leaders?

The second is: given the numerous injustices and the massacre that Mugabe presided over in his 37 years in power, how do African leaders wish to remember the 20,000 people killed in Mugabe's war on his own people in the 1980s? If we celebrate the perpetrator of these killings, can we prevent another massacre when it comes knocking?

Over the past three weeks we have seen Africa's new-generation leaders, from Kenya's Uhuru Kenyatta to our own Cyril Ramaphosa, rush to Harare to sing Mugabe's praises.

They were accompanied by Mugabe's contemporaries such as former Ghanaian president Jerry Rawlings.

Mugabe's passing is a classic case of how the lives of ordinary Africans don't matter to us except when it is fashionable and it is on public platforms just before an election.

Between 1982 and 1987, Mugabe deployed his North Korea-trained Fifth Brigade in the south and midlands of Zimbabwe to quell fighting between his supporters and those of Joshua Nkomo. Best estimates are that 20,000 black Zimbabweans were killed in that period.

For some perspective, between 1964 and 1980 when the people of Zimbabwe fought the white supremacist government of Rhodesia, 8,000 black and 468 white civilians were killed.

So, when we sing the praises of Mugabe, what are we saying about the lives of the 20,000 who died in those massacres between 1982 and 1987? Were their lives worthless, lacking in meaning?

Did they not have mothers, fathers, children, lovers or friends? Does no-one miss them?

Do their lives not matter? When we exalt their killer, what do we say about Mugabe's victims? How do we preserve their memories? How do we ensure that their massacre is never repeated?

And here is the greatest sin committed by those who have been singing the praises of Mugabe. They are trying to erase those 20,000 black lives from our memory and our consciousness. They are not merely trying to say that those lives don't matter. They are saying they never existed.

This is how massacres and atrocities are initiated and repeated - we remove all memory of what humans can do to each other and we pretend that this never happened.

Crucially, we tell those who have these instincts and the rhetorical power to drive crowds to assault and murder that they can go ahead and do what Mugabe and his ilk have done and still do.

Why? Because they will get away with it. Because when they die we will dance around their graves and say they are heroes. Mugabe was prime minister and head of government when 20,000 black Zimbabweans were murdered in his own country by his own brutal forces. I have not even touched on what Mugabe did to black lives in the 2000s.