Frankie Boyle has been debated on this site many times.
His appeal boils (no pun intended!) down to this - there are a section of people who think that the unsayable and socially tabboo subjects make for a kind of entertainment - where people laugh, but with their hands over their mouths because of the shock of what they have heard.
I would personally have a serious look at my sense of humour if I thought FB was amusing. People 'laugh' as a release of tension - someone who has had a narrow miss in a car will often laugh as a reaction, but it has nothing to do with being amused.
There is a school of thought that nothing is tabboo, and anything can be made to be humourous if people choose it to be so - and that is the bedrock of Boyle's career, and the reasoning of his audiences.
The fact is, just because people will pay to see and hear something does not mean it is not morally repugnant to the vast majority of society.
You could apply electric shocks to puppies and get a paying audience for it - the means does not justify the end in a civilised soceity.
Thanks to our laudible approach to free speech, Boyle is allowed to say the things he does on stage and on DVD, and people are allowed to pay to indulge their pleasure at him doing so.
However, Channel 4, the last bastion of 'alternative' humour have cut all ties with Boyle over just this sort of statement, and he will not be seen again on mainstream tv any time soon.
I would defend Boyle's right to practice his trade as a commedian - but for me, and a larger majority than his audiences, he commits the cardinal sin for any commedian -
it's not that me makes deeply offensive and upsetting coments about vulnerable people in our society, it's simply that in terms of commedy, he is about as amusing as dysentry on a coach holiday. Frankie Boyle is not funny, which makes he raison d'etre seriously flawed and hopefully his time as as success if appropriately limited.