What irks me is we've just had five years of chaos and economic crisis, because so many former Labour voters (mostly Boomers) decided they couldn't bear Corbyn's internationalism, and switched to voting Tory. And the verdict from the centrists is that that's Corbyn's fault, for not being sufficiently pro-imperialism and pro-racism to appeal to those voters.
I wasn't a huge fan of Corbyn, but it was pretty clear that he was far preferable to the alternative.
Yet when it happens the other way round, when leftists defect and either stay home or vote for a fringe party, because they baulk at the racism and imperialism of the 'centrists', then that is apparently the fault of those leftist voters for failing to hold their noses and vote for the centrist anyway, not of the centrist candidate for failing to appeal to those voters.
It seems to me to be a double-standard.
It's always the left's responsibility to back the centre-right, to keep out the far right. But the favour is never, ever, returned - when it comes to it, so-called centrists always decide they'd rather have the far-right in power than support a leftist.