Your description of successions of tyrannies is a truism. What's more instructive is how tyrannies come to be, and how they develop. A strong man rises to power in response to a perceived need. They usually have popular support. They then cement their power with a monopoly of the organs of power; in ancient times, this means a professional military, preferably mercenary. They then reinforce this with a campaign against a chosen "other".
Modern day nations have professional militaries separate from the ruler in power. However, there are other organs of power, ranging from the executive (the most important in this context) to the lawmakers and the courts and the media. In modern extremist politics, the executive and the media are what is important, as one does the work while the other suppresses dissent. The campaign is for some kind of identity, with any dissenters dubbed traitors.
Trump followers, Brexit followers, Corbyn followers all follow this blueprint.
Corbyn's anti-semitism stems from his Marcist readings, which themselves were reflective of Marx's times. That he's enabled it in the Labour party is because he's used to the workings of the fringes, and institutionalised everything is how they work. He is unpleasant, but his anti-semitism is not an existential threat to the UK. The abuse of democracy by Corbyn on the one hand, but far more so by Bannon's Trump and Brexit brigades on the other, is an existential threat to the UK. I described what I deem to be moderate politics from the voter's perspective. Do you agree with it? Or are you going to handwave it with "I have to say, I went through New Labour's education system, that was pretty terrible." NB. I didn't describe any political position. I described the necessary environment for reasonable politics to exist.
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