We have known this principle for a very long time. “Every kingdom divided against itself is brought to desolation; and every city or house divided against itself shall not stand”. (Matthew 12:25)
There is a fine line to be drawn between loyal opposition and actively undermining the policies of one’s country.
The spectrum of loyalty ranges from,“My country, right or wrong,” at one extreme, to “My way or the highway,” at the other. Those who espouse the latter position are so utterly confident of the correctness of their position that they despise those who disagree with them and can never be reconciled to losing a democratic vote.
The similarities between Putin, who could not accept the removal of his Ukrainian puppet and immediately began scheming to recover by force what he could not have any other way, and the relatively small number of Extreme Remainers in the UK who were, and still are, determined to reverse a popular vote, are quite striking, even if the violence employed by the latter is, fortunately, confined to language.
Immediate resort to abuse, with no attempt at reasoning, is common to both. Brexiteers are no more stupid than Zelensky is Nazi, but caricaturing your opponent rather than treating him as a human being with legitimate rights and aspirations, makes it easier both to hate and to incite hatred.
Clinging to a past that, if it ever existed at all, is viewed through rose-tinted spectacles, holding grudges long after the justification has gone, wilfully misinterpreting any and every event as proof of your own prejudice, and obstinately refusing to adapt and advance are also common characteristics.
At the very least, this sort of attitude is tedious, frustrating and insulting to those who don’t share it. At the worst it will destroy a society rather than see it change in any direction other than the desired one.
And in the end, some people would rather sit amidst the rubble (which in one case may be metaphorical) and say ‘I told you so,’ than share in a prosperous future that is not achieved by their desired method.
I don’t know whether this is what the PM was saying. It’s just the direction my thoughts took after seeing the question.