"Beyond a reasonable doubt" is a very high bar to match. Certainly way higher than would be expected of even the most respectable newspaper, for example.
It's a reasonable bar to ask for before you start demonizing someone in front of millions of people.
But let's be honest, Oliver didn't hate Murray because of the mine disaster, he hated Murray for mining coal. The mine disaster (responsibility for which wasn't even proven) was all LWT could dig up.
And the audience will pretty much hate anyone Oliver tells them to hate. That's why they watch - to enjoy their Two Minutes Hate.