The BBC knew he had been arrested, but that means nothing. He might have been not guilty, and you can't sack anyone on mere allegations. They say they would have fired him if and when he had been charged, but he resigned before then.
You can't blame the BBC for keeping anything quiet. There are legal restrictions on they an and cannot report in these cases. It isn't like a social media witch hunt (compare the EDL idiots at Southport yesterday).
I think you are right. However challenging, we must all follow and passionately protect the mantra ‘innocent until proven guilty’. That’s a grown up principal that social media has abandoned with often tragic consequences