I've always been surprised by the hatred the Left has for the Kochs, when the Kochs are moderate to liberal on most social issues. While Bernie Sanders has put economic Leftism center stage, as a general rule, liberals today care much more about social, racial and cultural radicalism than they do about economic socialism. They're willing to forgive Bill Clinton for tax cuts and welfare reform because Clinton supported trendy causes like gays in the military and embraced the "first black president" label. They can forgive JFK's (general) free market instincts and opposition to a growing welfare state because he was a liberal on desegregation, etc.
Since social and racial radicalism is the defining litmus test for the Left, it's still a mystery as to why the socially moderate Kochs became their number one bogeyman (or bogeymen).
Because every tyrant knows you’ve got to have a scapegoat, and if there isn’t one, you make one up.