It has long been the conventional wisdom of politicians that Homo economicus - Economic Man - is the best and a sufficient description of modern people. In other words, that the masses are solely concerned with money.
This in turn means that the most effective bribe is presumed to be more money, and the most effective threat is presumed to be a decline in the 'standard of living' (defined economically). And, since the future is uncertain; the most effective carrots and sticks were presumed to be immediate, short-term - money-in-the-pocket incentives.
Thus were Western populations controlled.
The vote to Leave the European Union overturned this assumption - with millions of people voting against their short-medium term economic interests - which meant that the Ruling Class suddenly lost confidence in their ability to manipulated the masses with monetary bribes and threats.
Hence the air of panic; and hence the instantaneous use of vilification. By projection of their own motivations; the ruling class automatically assume that:
1. The masses are almost-entirely motivated by money; and 2. that the only motivation even-more powerful than money is hatred.
This is how it is for the Establishment, and they naturally assume it is the same for everyone else. They are mostly motivated by financial greed; but this can be overcome by their loathing for the mass majority of British people - for example exemplified their core strategic policy of open-ended mass immigration to destroy the lives of, then replace, the native population.
For the British rulers, crushing the native masses is a moral crusade.
However, mass immigration will destroy the long-term prosperity of the nationa, hence the Establishment - but they support it anyway because their hatred is even stronger than their greed.
Therefore - for the Establishment, the Only comprehensible and plausible reason that the mass of British people would overcome their greed is hatred: hatred of foreigners - racism.
It is literally off-the-map and incomprehensible to the Ruling Class that people might want to leave the European Union from love - such as love nation and place, deep attachment to a way of life, loyalty to a sense of history and ancestry.
Our rulers cannot believe this because they themselves do not experience such emotions.
As Walter Scott wrote:
Breathes there the man, with soul so dead,
Who never to himself hath said,
This is my own, my native land!
Whose heart hath ne'er within him burn'd,
As home his footsteps he hath turn'd
From wandering on a foreign strand!
Yes indeed, breathes exactly such many a man and woman; breathes such the entirety of our ruling Establishment including almost the entirety of the Houses of Parliament; and breathes such the controllers of the apparatus of government and law.
And what shall become of them?
If such there breathe, go, mark him well;
For him no Minstrel raptures swell;
High though his titles, proud his name,
Boundless his wealth as wish can claim;
Despite those titles, power, and pelf,
The wretch, concentred all in self,
Living, shall forfeit fair renown,
And, doubly dying, shall go down
To the vile dust, from whence he sprung,
Unwept, unhonour'd, and unsung.