Leftism (in its modern Western form of the New Left/ Political Correctness of Social Justice Warriors) is essentially atheism - hence strictly insane.
I shall term it PC insanity.
Atheism leads (inevitably, albeit by stages, incrementally) to a species of insanity - and it is important to understand the nature of this endemic madness.
Atheism leads to insanity because it entails a denial and rejection of that which is intrinsic to Man: an awareness of the divine and universal. Hence there is an assertion of existential isolation - consequently futility. Despair and a suicidal self-hatred is the outcome.
However, on the way to this outcome there is the PC insanity, a pervasive psychosis, that we see all around us. Political Correctness is not identical with any specific psychosis known to mainstream psychiatry - but has elements of all four of the primary types: schizophrenia, mania, melancholia (depression) and the delusional disorders.
With schizophrenia PC insanity shares 'paranoia' - i.e. delusional self-awareness, persecutory ideas and the belief that everything is about 'me'; also an underlying existential fear.
With mania PC insanity shares aggression, irritability, interfering querulousness, extreme (but brittle) grandiosity and pride, indiscriminate and fickle physical lust; and a frantic and distractible energy.
With melancholia PC insanity shares guilt, despair and the yearning for escape into suicide (in the belief that death is the end of all consciousness).
With the delusional disorders (e.g. delusional jealousy, persecution, erotomania) PC insanity exhibits resentment and projection: attributing to others that which is most powerfully experienced and feared in oneself; and sometimes 'dysmorphic' somatic delusions of bodily abnormality - the fixed and false belief that something is physically 'wrong' that needs to be surgically 'corrected'.
Please do not imagine I am joking about this! The modern mainstream West really is insane, and this is reflected in widespread beliefs and behaviours that truly are delusional in their nature, conviction and intensity.
Fortunately PC insanity is curable. And the treatment is available to anybody and everybody, free of charge. And is instantaneously effective (although it may take a considerable time, perhaps longer than a mortal lifetime, to make a full recovery).
But the cure is available only from a single provider, who has a monopoly on production and distribution: His name (make a note of it) is Jesus Christ.