Hardly a secret. I don't know of anybody who thinks Mugabe is any sort of good guy.
The problem with Mugabe is that he came to power (via democratic election) in 1980, and was viewed at the time with high hopes as a progressive African leader.
He gradually devolved over time into an autocratic despot, concerned above all with retaining power and control, no matter at what cost to the country.
And as such he presents a severe problem and embarrassment for liberals. Rhodesia was a classic example of paternalistic colonialism -- 3 or 4% of the population was white, but owned 97% of the land. Blacks were treated as second class citizens, without full rights or opportunities.
Conservatives pointed out, however, that black citizens were far better off in Rhodesia than they were in neighboring black led countries. They predicted disaster would arrive with black majority rule and it turned out they were right.
Mugabe's supposed land reform program was cheered by those who saw the status quo as racist and inherently unfair. (Which it was) However the "reform" turned out to be mostly a crony driven division of spoils, with land handed over to political allies and friends who were totally incapable of farming it.
The long term result has been to transform Zimbabwe from perhaps the most prosperous nation in Africa into a nation on the brink of collapse today.
There's a cautionary tale here, but I'm not sure what it is.
P.S. I'm not as informed about the history of the country as I might be, so my percentages may be incorrect and I welcome corrections.