To blame for opposing white minority rule?

In a different mode the question has been brought up once before here. Do those who supported the coming of majority rule in Zimbabwe bear some responsibility for what Mugabe has since done to that country? In his column today, Max Hastings poses it again:

The tragedy of Zimbabwe makes some of us search our own consciences, back to the years of white supremacy...
.....
Because I was one of those who passionately opposed the white regime and supported black majority rule, I often ask myself whether I bear a minuscule share of responsibility for Mugabe. Reading Godwin's tale of tragedy, of misgovernment on an epic scale, it is difficult to deny that whatever black Rhodesians endured under Smith is less than they have suffered under Mugabe.

Hastings gives no direct answer to his own question, saying only that...

[N]othing can make those who saw white minority rule in its naked ugliness lament its passing.

To my mind, the answer is no. Moral responsibility is a complex topic, and I don't intend to go into it here. But, in general, it can't be the case that you're morally responsible for everything you play some causal part in bringing about. If A and B are happily married, and then A dumps B for another, leading to B some time down the line marrying C and later, with C, having D, their only beloved offspring; and if D goes on to become a murderer... A isn't responsible, not even a little bit, for the murder(s) D commits. More particularly, those who supported the end of white minority rule in Rhodesia (as was), aren't responsible for the crimes of Mugabe unless it can be shown that these are the foreseeable consequence of majority rule as such, or of black majority rule - in the latter case a plainly racist assumption - rather than being the result of the more specific history of Mugabe's regime and, under that heading, of the crimes he and his cronies have committed. Why should a supporter of democracy in Zimbabwe be held responsible for the actions of others who have wilfully wrecked it?

On another point, it isn't clear to me why Max Hastings should present compassion for black Zimbabweans and pity for 'decent' white Zimbabweans as competing with one another - as if a person couldn't feel both.