Far-left and far-right ideologies have more in common than many people realize (including the people within those factions). They are both based on the principle on low tolerance, and as such they are well-aligned on the idea of strict enforcement of their ideologies.
There are some hilarious misconceptions that members of those factions have about their own ideologies. Far-left is against the police brutality, but there is a 100 year history of perfect correlation between leftist regimes and policy brutality.
Far-right is against government interventions in all economic matters, but that also has never materialized anywhere else.
The bottom line is that anything that's far-something requires suppression of the society's natural tendency to return to the center.
The Wilson and Attlee governments in the UK would be very surprised to hear there's a "100 year history of perfect correlation".
They were certainly leftist. Many would consider them far leftist today. (Of course they weren't, but that doesn't mean the label wouldn't be applied.)
Neither was legendary for police brutality. That came later, with Thatcher's response to the Miner's Strike and the poll tax riots - among others.
I have a hard time considering a government that ruled over and fought bitterly to protect a global capitalist empire as truly 'leftist,' unlike the UK's geopolitical enemies of the time.
It is also likely that subjects of certain British colonies would have a substantially different opinion on police violence.
Where is the line at to be drawn between nationalism and fascist ultra nationalism? The rise in nationalism in many countries is one thing, but as that nationalism becomes stronger it is too easy to see it as drifting into fascist territory.