I abhor the American culture of everyone suing everyone else for all sorts of real and imaginary stuff but it might work in this case.
If the guy could sue this Sonko fellow for all kind of stuff - mental distress, loss of business, public humiliation and anything else his lawyer comes up with and is awarded approx. 100m, it might tame Sonko and his ilk. I know you are wondering 100m??? Yeah 100m!! That's what happens in the west. The judge or the jury make sure you feel the pinch. The richer you are, the higher the award! Now, Sonko might be rich [by Kenyan standards] but he would surely feel the pinch of a 100m - even 20m.
That might not happen in Kenya any time soon though [New constitution not withstanding]. You know what they say: "Why hire a lawyer when you can buy the judge?". Sonko would buy everyone including the cleaners at the high court and you might find yourself paying him the [inflated] cost he incurred due to the lawsuit!
Never count on making a good sale. Have the purchase price be so attractive that even a mediocre sale gives good returns.