Are we all going to stand by and do nothing because this is mass murder by socialism?
Socialism is a crime against humanity and, as we can see here, can rise to the level of mass murder. This is not a new invention. Mass murder of targeted populations by starvation has happened before.
At this point - yes!
We - the US - have shipped tons of grain that has been turned down by Zim and others in Africa in response (for what reason I cannot imagine) to politically correct anti-progress, anti-American, anti-science, ideology.
We handed them a rope and they refused it because it suited their purposes to rebut us and to eliminate their internal opposition. (A twofer)
So, let them go about destroying themselves, let the rest of Africa and the world mull the logic of that action, let them take sides.
Oh, and since that evil GM grain does in fact belong to us, and since no one in Africa wants it - I'd burn it on site and let them figure out that a non-socialist society can produce a surplus and waste in any way it wants. (Meaning we don't have to rely on their assistance if all we want to do is waste food or fortune.)