I haven't heard of the term 'spiky writer' either. It certainly isn't a common collocation, but I can imagine what is meant. If someone is 'spiky', they're difficult to deal with - sharp and argumentative, like trying to get hold of a hedgehog! Here's a page of synonyms for 'spiky' in this sense. Take your pick! http://www.thesaurus.com/browse/spiky?s=t

Writers who are disaffected are likely to be writing in a way that criticises the status quo, taking shots at the establshment etc. While I haven't heart 'spiky' used in this context before, given the whole sentence I would guess that it is being used as a synonym for 'edgy', taking shots at the mainstream, etc. Is that helpful?