Killing other humans is often justified. For instance, it would be completely justified to kill someone who was in the process of shooting up a school.
In the same way, billionaires are guilty of causing the deaths of millions of people through their hoarding of necessities. Killing the billionaires would allow this wealth to be redistributed, saving potentially millions of lives.
That's a bad comparison. The Wikipedia decision was made specifically because the experts -- i.e actual scholars of genocide and war crimes -- have a very widely held consensus that a genocide is occurring.
Do you disagree with the experts?