I sincerely doubt the government of Zimbabwe, a nation of about 12 million people, is worried about a couple thousand white people rioting -- most have already left and those who remain are scared to death (or are actually being killed). It's a pretty safe bet they are more concerned about breaking up protests by the Mashona (about 9 million people) and Matabele (about 3 million people) protesting against Robert Mugabe's crooked election tactics and repressive government or in support of opposition leader Morgan Tsvangirai, who is currently facing treason charges in that messed-up country.
Considering the number of people who are routinely shot, dismembered, disemboweled, burned or impaled to death in Zimbabwe these days, armored vehicles spraying cold water on a hot crowd is hardly a mortal threat.
Imal
There is more to it than that. These are armored vehicles with gun ports. Take a look at this baby. And we're talking about Mugabe--a stone cold killer. The "we're only selling water cannons" is a dodge to make the sale look halfway moral. Shipping heavier equipment or tanks would only infuriate the EU, which doesn't like this deal, more.
Check out #31. Africa is fascinating to research. Lots of arms flowing in from the Ukraine which are handled by Israeli nationals. Necessary to use Babelfish to translate French in many cases.