I would suggest it depends what it is – my kids are now 6 and 3, and CBeebies will be on for anything up to 6 hours a day BUT it is often only a background noise, and both will happily turn it off to go and play, paint, read, help with the cooking etc. Yes, we do sometimes use TV to keep them occupied while we get on with jobs around the house.
Both kids are sociable, bright, articulate and knowledgable compared to their peer group.
However, I regularly go to houses (in connection with work) where kids spend a similar amount of time in front of constant cartoons, or the millionth rerun of their favourite DVD or – lord help them – Jeremy Kyle etc, and you can see that these poor kids are destined to follow in the footsteps of their chav scum parents.
I wouldn't worry so much about the quantity of TV they watch rather than the quality, and it's role within a wider family and learning environment.
Though I'm prepared to be shouted down by all the hair shirt wearing Guadianistas on here 🙄