Frankie Boyle's a pretty interesting case.
Back in the early to mid-00s there was a big trend of really nasty comedy, where people thought the funniest thing you could joke about was someone being gay, trans, poor, disabled etc.
Boyle on Mock the Week was right at the forefront of that, along with Catherine Tate and Little Britain, and I think it's really interesting looking back at just how badly those shows and characters have aged.
The shock factor was what people laughed at, and that brand of comic had to keep making more and more shocking jokes. So over the space of a couple of years he goes from telling "I can't believe he's got away with that" jokes about Thatcher or Gordon Brown or the Royals, to making his 8 year old Harvey Price his public punching bag. When you look back at it 15 years later when it's no longer shocking...they do not stand up, they're just not good jokes.
I think if he's honest he'd probably agree that this shock jock persona got away from him and his comedy is better now it's not being written with the sole aim of being as offensive as possible.
By the way, Boyle used to write Jimmy Carr's jokes for him, so quite fitting he's popped up here.