Ideological Segregation consists in selectively mixing truth and falsehoods together and presenting them as an interconnected whole, thus forcing people to either accept them or reject them all in block.
In order to mantain its power, every ruling elite needs an ideology or narrative that pushes people to support their power.
However, any ideology that is almost exclusively made up of falsehoods is too easy to unmask and, by contrast, the opposite one too easy to be recognized as true; as long as the discourse remains so clearly divided, sooner or later the entire population will eventually flee from the regressive ideology and flock to the liberating one, no matter the amount of propaganda employed to defend the first and/or attack the latter.
For this reason, the modern ideologies and narratives are systematically manufactured in order never be *entirely* wrong, but to always include a specific amount of truths among the lies: they always speak the truth on specific issues and at the same time lie about other ones, in such a way to make the lies seem inherently dependent from the truths (by employing profuse amount of fallacies and other manipulation tactics) in order to present this mix of truths and falsehoods as a coherent, monolithic whole. In this way, any weak-minded person that recognizes the truths will be manipulated into agreeing with the lies too; instead, those who recognize the lies, will also reject the truths, coming to a diametrally opposite opinion that is right where the mainstream one was wrong, but wrong where the mainstream was right. Since, logically speaking, true and false = false, the result is that both sides are guaranteed to always end up with a wrong worldview and thus never be able to achieve true emancipation.
The additional advantage of having truths and lies cleverly mixed is that, by confirmation bias, each side of the debate will only see the truths on its own side, and only the lies on the opposite one, gaining constant confirmation that its own side is the right one and the other is the enemy, with the effect of promoting division and infighting among them, and preventing them from any constructive cooperation towards the truth.