dholliday
deconstructed rep
Tbf as mad as I find some of Soft's posts, that's as unquantifiable and absolutist a statement as you're accusing him of making.
I think it is quantifiable in that it's known and documented how many on the traditional Left feel pushed out by a vocal nutty minority on the extreme Left. This pushing can become significant if it results in those being pushed not voting for traditional Left figures as those figures become less vote-friendly due to them having to bow more than usual to the extremists, or due to media propaganda (the Corbyn-hate in liberal newspapers comes ostensibly from what we now would refer to as the extreme, or Far, Left).
I can even link some articles on just this line of thinking:
Extreme Left is destroying the Labour Party
Bernie Sanders Is Not the Left (yes, Sanders isn't even Left enough)
This one's kinda related: How the Left Lost Its Mind
We see it here on this thread where centrist has become a dirty word, even code for actually meaning right-wing (which is just an insult nowadays, it barely means anything anymore). As being centrist or centre-left doesn't equals Far Left it gets attacked for not being part of the club. It gets labelled as belonging to the other side right there on the Right. As if there can be only two forms of thinking.
The Far Left are addicted to this kind of identity politics, and it may mean we won't see a Corbyn-led Labour government. That's worth pointing out.

