I am not keen on parts of it either, but nevertheless, I do wonder if it is partly true.
Yeah, parts of it are true, in the sense of truisms. Do people pay more attention to causes that threaten to, or actually do, blow shit up? Yes, but that's hardly a unique failing of the left: I might be wildly out on a limb here, but the Muslim community in the UK was treated with kid gloves during the Rushdie affair, and it's hard to see an argument that says that the government of the era were milk and water liberals, given that in 198889 Thatcher was pretty much at the rancid apogee of her reign. Even in the US, large amounts of peaceful middle-class protest over Vietnam achieved pretty much nothing, but the rioting in inner city black neighbourhoods in the same period drew forth substantial social and political change; the president 196874 was Tricky Dicky, again hardly a liberal.
I think it's also close to a truism that the left, in particular, has a lot of posh boys who don't want to get their hands dirty or their expensive shoes scuffed, but have a massive and vaguely homoerotic hard-on for rough boys who don't mind a fight. Corbyn and McDonnell would be a clear case in point here, in that they appear to have spent too much time masturbating over pictures of bearded ruffians from Hamas (oh, he may be a naughty boy, but he's so authentic), but it's hardly unusual: Seamus Milne and George Galloway both have massive boy-crushes on Stalin ("you can't make an omelette without breaking eggs", and so on) and he died before they were born. Wet kids who got beaten up in he playground fantasise about revenge on those that laughed at them, and nothing says revenge quite like the systematic killing of entire social classes.
Sartre, I think it was, skewered anti-Semitism as being the ideology that means that even a halfwit can be part of an elite, and it was Thomas Mann who summed up their thinking as being "‘I might be nothing, but at least I am not a Jew.’" Corbyn, McDonnell and Livingstone share inadequate educations which I suspect make them both undiscerning (cf. Brenner, who is a fool) and bitter (cf. Jews, what with all the controlling the media and so on). Milne and Abbott don't have that excuse, but both appear desperate to be respected as forces: did you see Abbott's pedantic correction of Marr this morning over the precise wording of her title (hint: a shadow minister has about the same power as someone working the tills at Sainsbury)?