Well, I'll have a go but remember it's only my opinion so will benefit from feedback. It will also go on for a bit so I've done my best to give a summary in the next paragraph as this is probably as far as you'll get into it.
The material atheist perspective is an evolutionary one - the survival of the fittest. Think here of the dinosaurs - they existed merely to consume and breed. From a human perspective 'everything is permitted'. That which is strong is moral and that which is weak is immoral - strength here defined as the ability to control, consume and exploit. De Sade did nothing wrong from this point of view.
Think of Selfish Gene Theory for example:
'The gene-centred view of evolution that Dawkins championed and crystallized is now central both to evolutionary theorizing and to lay commentaries on natural history such as wildlife documentaries.
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What stood out was Dawkins's radical insistence that the digital information in a gene is effectively immortal and must be the primary unit of selection. No other unit shows such persistence — not chromosomes, not individuals, not groups and not species.
These are ephemeral vehicles for genes'
In retrospect: The Selfish Gene - Nature
We can see this in "woke" ideology - which rests on an atheist materialist foundation.
The rules of society (from this view) are impositions of power implemented by those with the whip hand. There is no immanent moral model to bring into effect other than that of the supremacy of power.
Plato had a character,
Thrasymachus, whose position was that ' justice is conventionally established by the strong, in order that the weak will serve the interests of the strong. The strong themselves, on this view, are better off disregarding justice and serving their own interests directly.' (He was Plato's personification of tyranny in this dialogue)
And so we see the insistence on collective action, with the individual as merely a component unit, as the primary definition of identity. The "weak" must bind together to fight for power with the "strong". There is no moral code of conduct to follow - politics is an affair of tooth and claw. That is what gives them the justification to act lawlessly - shout down critics, engage in riot, act preferentially, desecrate, lie, thieve and assault etc.
The fact that the other guy has resources that you want is what is immoral - there are no ethics here. It's a criminal psychology.
So, how does this affect national communities? Well, first, allow me to say that we are bound to act justly and wisely towards everyone by the precepts of our own tradition while, nevertheless, acting with due prudence and practicality.
A national heritage includes codes of moral behaviour that do not immediately arise in superficial contact but take time - often long periods - to develop and inculcate.
Take for example malicious damage. Toddlers are renowned for malicious damage during temper tantrums but it is abhorred in older children and adults. One may not act out one's tempest of negative emotions on someone else's property, interests or peace of mind. It is sub-adult and
inferior behaviour not to observe prudent boundaries.
Malicious damage here does not simply refer to vandalism but also to inaction. If someone was being gaslit, burgled or embezzled, and you knew it was going on but they were unaware or unsure, then there is a moral duty for you to advise them - to omit to do so is immoral. To be moral is to be a man or a woman, to be immoral is to be merely a male or a female.
There are deep prohibitions on such things as malicious damage in established communities and these rules enable a high trust society to operate. Not only does a high trust society lower costs of transactions and facilitate prosperity, it also enables a higher level of operation - a 'transcendence'. Peace produces stepped evolutionary change by disarming anxiety.
Think of something along the lines of moving from the steam engine to the internal combustion engine - flight was impossible without a petrol fueled motor. The great world religions saw enormous leaps in civilisation exactly as an output of high trust improvements. Low trust encourages enslavement, high trust encourages liberty. Personal rights become increasingly possible as a result.
With trust it is then possible to establish a society that transcends the vulgar survivalism, of say a pirate settlement or a drug infested slum, by being in an environment where one can successfully engage in productive activity without it deteriorating into
a cat fight. This is why low trust types, while they may be sly, are limited in scope and high trust types, while they may be less saavy to dissimulation, are interesting - realms open to them that were previously beyond their grasp.
The concern that Mr P is articulating is that an engorged influx of individuals from low trust societies will reproduce the same conditions in our society as that from which they fled. Integration becomes overwhelmed. Sweden is a point in case here. Its current condition is precisely an outcome of the degradation of a high trust cultural superstructure - there's a blurred vision that inhibits decisive countermeasures to deviant behaviour.
This is not an objection to the individual migrants (these may be good or bad people each in and of themselves) but in the overloading of capacity and the creation of pockets of people who view their hosts as targets of cynical exploitation - as weak and stupid fools who want to be told lies in return for their stuff and daughters. The concept of moral dignity in high trust societies (something which has a very strong influence on normal action) is a nonsense to them.
Furthermore, high trust exists in pockets outside which the base mechanisms of biology rule - see chimps as an illustration here. This is a fact of biological existence - the universalism of God
is a relevation of a higher condition of existance (analogous to the difference of condition between a sponge and a rocket scientist).
Now, I have to include here that I would choose to be in the company of a good Christian African over that of a wicked criminal Irishman every time. That criminal Irishman might appeal to some racial intersection but the deciding factor in the choice would be the difference in integrity between the two. Thus, I would have no problem as describing the criminal as verminous human filth while I would consider it a disgrace to describe the Christian as such. The ultimate decider between people is good and bad, not declared affiliation.
A primary definition of a national unit by "race" replaces community with breeding pool. This places it in the sphere of evolutionary theory and, as such, makes a nonsense of anything other than the maintenance of genes. There is no science, that I'm aware of, that has identified the moral sense in a particular chromosome and it is the moral sense that unlocks access to civilised life and a superior human condition. If one is truly concerned about living the good life then it is the formations that nurture wisdom and good behaviour that we should seek to conserve and embellish. A race based definition of good and bad is a feign for the self serving and malign.