Cultural point about the UK. When we are being sarcastic, we sometimes leave out words in relation to what other people are claiming. So the proper version is:
“[The UK establishment claim that] ISIS and even Russia are barbarians, but [they hypocritically insist, by contrast, that] dodgy UK politicos merely make the proverbial time-honored ‘honest mistakes.’”
That’s really what I meant. Sorry for the ambiguity.