Many, most, people do not notice that Leftism is primarily and intrinsically anti-Christian - and one reason they don't notice is that in the early decades of English Leftism, and even extending into a few people still alive today, there were real Christians who were Leftists - Christian Socialists.
In the Nineteenth century into the twentieth there was FD Maurice, HH Kelly, Charles Gore (great and Holy Anglicans), there was the Anglo-Catholic movement - and there was an economist called RH Tawney who led to a school of 'ethical socialism' which included some people I know as friends, including the late Norman Dennis.
Does Christian Socialism refute the idea that the Left is intrinsically anti-Christian?
No it doesn't.
English Socialism is based upon an error, indeed multiple errors - the primary error being that the industrial revolution - while creating a minority of extremely wealthy individuals, led to an economic decline for the working class.
In other words, the error was that the industrial revolution led to increased economic inequality, and that therefore the solution was greater equality.
In reality, the opposite was the case. The industrial revolution involved population growth and productivity growth - so per capita wealth increased, and the greatest share went to the poor.
For perhaps the first time in human history, from the time of the industrial revolution, the poor had more surviving children than the rich.
English socialism was an error simply because the new urban poverty was concentrated and public in its squalor hence impossible to overlook, while the much more severe rural poverty was dispersed, private, invisible.
Upper class people of a type disposed towards socialism simply did not notice poverty when it was most severe - when the children of peasants (no matter how many were born) pretty much all died of starvation or disease, and only those born to wealthier parents had a realistic chance of surviving to adulthood.
So English socialism had a twin basis in economic error, and a misplaced rural nostalgia.
The economics was a plain error, since if it is economics that you are worried about, it is capitalism which has improved the condition of the poor - not socialism.
The rural nostalgia (most notably of William Morris) was misplaced in so far as its focus was economic - urban conditions were indeed hellish, but they were considerably more prosperous overall.
If economics is to be the focus, the bottom line was that the urban poor had more to eat. The benefits of rural living are not economic.
Of course, even though Leftism in its English socialist form was based on error - many of its motivations were good.
But the stubborn refusal to admit the foundational economic error, decade after decade, utterly corrupted socialism.
The focus on alleviating poverty shifted as the poverty was progressively abolished by the continued operations of the industrial revolution - instead of the ancient definition of poverty as (primarily) starvation and lack of clothes and shelter; poverty was redefined as relative, as a matter of inequality - and inequality, difference, was newly defined as intrinsically unjust.
The least-wealthy were the new poor - among a population living among universal luxury, those with fewest, or lowest status, luxuries became 'the poor'.
Yet socialism contrived to retain, by educational propaganda and the mass media, the same angry zeal and impatience concerning relative poverty as has driven it when the concern was with death by starvation.
Instewad of being angry about actual poverty; Leftists were now angry, very angry, about injustice - which could be detected wherever needed; defined and re-defined at convenience.
In the early 20th century, Socialism became an economic theory (the 'command economy' in communism, or the 'planned economy' in Britain), in rivalry to 'capitalism', for improving economic growth and for a 'fairer' distribution (failing to recognise that the distribution of economic benefits of the industrial revolution was from its very origin already strongly egalitarian).
What has all this to do with Christianity?
Certainly socialism does not come from Christianity - since there were some 1800 years of Christianity before socialism.
Certainly socialism was not a legitimate Christian response to the new spiritual problems of the industrial revolution - since socialism is an economic theory, and the industrial revolution improved the economic conditions of the poor. The idea that socialism would help was based on a mistake.
Christianity does not legitimately come from socialism, not even in the new and specific conditions since the industrial revolution - since an economic focus for life is an intrinsically anti-Christian stance.
The vast majority of devout Christians have not of course been Leftists (were indeed opposed to Leftist ideas); and the vast majority of committed Leftists have not of course been Christian (were indeed opposed to Christian ideals).
So the Christian Socialists are a tiny minority, where these two separate systems overlap...
Are they correct or deluded?
They are deluded, Christian Socialism is not a novel and coherent synthesis - but is merely (at best) two separate systems in the same mind: unintegrated, unintegrable.
Most often, Christian Socialism is a consequence of error, or a consequence of dishonesty.
But humans are error prone creatures - our information is incomplete and biased, and our reasoning is defective, and we are easily influenced.
Yet error - honest error - typically becomes obvious within a few decades.
"By their fruits shall ye know them" - and the fruits of Leftism are rapidly and reliably anti-Christian, as can be seen within one or at most two generations.
That Christian Socialism was a heresy was apparent within a few decades, the intrinsically anti-Christian nature of Leftism obvious in all Leftist controlled states within a few decades (sometimes even faster).
Therefore, the only Christian Socialism which is good, is that which is based upon an honest economic mistake due to ignorance - but the error of Leftist economics soon became dishonest, and in order to preserve Leftism the error had to be preserved - which led to systematic lying, and then (and now) to systematic and coercive imposition of lies.
So Leftism is now objectively evil - indeed by far the major source of societal evil in the world (by societal evil I mean added to the irreducible minimum from original sin).
Indeed it now looks as if Leftism was the greatest triumph of evil in the history of the world.
So Christian Socialism is (and always was) an oxymoron, self-contradictory, self-refuting - intrinsically destructive to the Christian element of the compound name.