I can understand Dan's frustration. He is of the view that the Labour Party had 18 years of pain before cottoning on to what needed doing to win power. It meant adopting policies closer to where the majority of voters sit on the political spectrum, it meant appearing strong on the core issues pertaining to voters' senses of self-security (i.e. the economy and defence), and it meant having a leader that could inspire confidence in those parts of the electorate most likely to cast their ballots. He was of the view that Ed Miliband wasn't up to it, and so it proved - though I doubt very much his preference would have turned out any better. And now with Jeremy at the helm, he believes the party as a whole have unlearned the lessons of the 80s and 90s. The reality is rather more complex than that, but our Dan has always had a penchant for black-and-white thinking smeared with a dollop of cynical empiricism.
Let's take his two big points in turn. Likening Jeremy to Enoch Powell was obviously intended to inflame. How dare a lifelong champion of anti-racism be likened to the poster boy for racists. The comparison, however, doesn't work that well. Whereas Powell was a "principled" and unapologetic champion of patrician Toryism which, nevertheless, was already moving towards the fringes of the party when he made his celebrated anti-immigration missive, you can see that Dan is desperately trying to map Jeremy onto him as someone equally as rigid and out-of-step with modern life. The key difference is that while Powell did and Jeremy does represent a real movement, Powell was ultimately an individualist who turned his back on the Tory Party over Europe and later returning as an Ulster Unionist MP. Jeremy, whatever one thinks of him, is a proper labour movement person who believes in the power of the collective. Corbyn fans threatening to leave if Jeremy goes, take note - the party is always bigger than the individual. So no, Dan's comparison doesn't really work - but then any old rope will do.
As it happens, this individualist feature is something Dan shares with the Corbyn supporters he despises: a preoccupation with purity. His whole piece drips with sanctimony, as if the leader, the MPs, the supporters are all morally responsible for the baby killing outrages IS are reportedly committing. Never mind that British jets haven't flown sorties against IS targets for several days, or that the whole campaign is a joke taking place solely for appearance's sake. Just like Jeremy's legion of keyboard warriors, Dan's participation in politics is almost entirely virtual. He, like they, sit on Twitter permanently aghast. He soaks up the media coverage and cannot understand why other members and, occasionally, the public are indifferent to the appalling coverage the leader attracts. Difference being he gets paid to write up his sense impressions of this rarefied world. That and occasionally worried Labour MPs and complementary Tories phone him for a gossip. Having imbibed and contributed extensively to the media characterisation of the party, he believes his own propaganda and holds the party to be unclean and repugnant. His stated intention to "stay and fight", which is why he rejoined in June, was somewhat undermined by his complete lack of party activity or attendance at meetings - you know, where the real action and debate in the Labour Party takes place.
Dan is a columnist who makes his living by writing comment. Nothing wrong with that. What Dan is not is, like celebrity members such as Robert Webb and Matt Forde who've made similar huffy exits, an activist, someone who voluntarily gives their time to fight for the politics they believe in vis a vis the public and/or fellow party members. Ultimately Dan's repeat resignation is symptomatic of centrist narcissism that says less about the Labour Party and more about him, his political immaturity, and his total lack of fortitude.