His grip on power is nearly unassailable. Since becoming president over two decades ago, he has extended constitutional term limits, shut down the free press and clamped down on dissent. Reporters have been driven into exile, even killed; opposition figures have been imprisoned or found dead. His country has been reduced to tyranny.

But this dictator isn’t a pariah, like Vladimir Putin of Russia or Bashar al-Assad of Syria. Instead, he’s one of the West’s best and most reliable friends: Paul Kagame, president of Rwanda. Since coming to power in 1994, Mr. Kagame has won his way into the West’s good graces. He’s been invited to speak — on human rights, no less — at universities such as Harvard, Yale and Oxford, and praised by prominent political leaders including Bill Clinton, Tony Blair and the former U.N. general secretary Ban Ki-moon.