Don't blame the BBC, they all worked for plenty of places that either turned a blind eye or never suspected anything untoward was going on. The offenders played the family entertainer card and it got them into lots of places and associated with all sorts of establishment figures (police, NHS, politicians, royalty). And the whole nation, aside from those who watch TV to slag off certain celebrities (OK, that's never gone out of fashion) were complicit. Because they were associated with a safe, cosy world of celebrity.
I notice there's a Mary Whitehouse documentary on BBC2 next week. There's a woman with a highly conservative outlook who never noticed horrendous abuse going on by her associates. I'd be very surprised if they don't mention it in the doc. A lot of the time it's just not expected, so... it's not ignored, exactly, it's just not picked up on at all. It is disturbing, but hindsight is 20/20 (and not even that in some cases).