Karl Marx, class war. Look for every possible difference in society, tell people about it, and tell them they're being persecuted. This took some genuine and some not so genuine problems in society and either way even when most of these problems had been addressed and dealt with by things like anti-discrimination laws they refused to go away. They make an art of searching meticulously for every possible group causing or suffering discrimination, letting them know, and even, in some cases like the disabled and many Muslims make rules about how to treat them whatever they actually want for themselves. And then they use or invent 'isms' to accuse anyone not on their side to demonise them regardless whether all they are doing is presenting a different opinion to the 'right' one. This has the main effect of setting groups in society against each other, and seeing those on the other side as the enemy, leading to such results as claiming 'all men are potential rapists' and looking for racism every time a white person opens their mouth.
So each formula works to destroy society, the working class despise the bourgeoisie, and are told never to trust them as they are slave owners, and rather than have aspirations to succeed mistrust anyone who has done well, especially those from their own backgrounds who have done so and as a result could be ostracised. The absence of such false or exaggerated differences allows people to be themselves and succeed or otherwise on their own unique merits, and not blame imaginary discrimination every time they fail, rather than the current fashion of playing the race or gender card each time a person gets stopped by the police, doesn't get a job, or a promotion. Instead of taking individual personal responsibility for being a unique person capable of doing anything and everything they could do, they look for trouble and assume anyone who does not offer them more than the average is discriminating against them, and anyone who does not give them anything has to be a racist or a sexist. This creates a permanent perception of 'them and us', the paranoid cloud hanging over their eyes seeing a group of men hanging around in the street at night as potential sex offendors, or any white person holding an interview or police officer being institutionally racist. As if an institution can even hold an opinion. The abandonment of individual values and opinions to the collective, 'The police are institutionally racist' 'Men are all potential rapists' etc simply means the 'victims' genuinely begin to believe huge groups of people, up to half society in the case of women, and nearly all of it if all white people are racists, and what does that do to their psychological makeup and welfare? It makes them see trouble all around them, which is responded to with a combination of fear and anger, and ends up with riots and wars. No one at all benefits from imaginary and false divisions, society becomes a collection of different 'them and us' groups, so a Muslim woman for instance can see both rapists, racists and religious bigots every time they go shopping in exactly the same people, and then think and act towards them as if they genuinely are at the extreme end.
The left basically work on principles of division and difference, and mistrust and suspicion of those who are not 'us', with their policies designed to force society to react as if these delusions are correct, attempting to outlaw any speech or opinions different from their prescribed templates, forcing companies and organisations to employ black people and women above white men and poor students above others for example, regardless of the individual's suitability for that position. Besides the obvious legalised discrimination the psychological effects of such attitudes are toxic to the individuals and society around them, seeing more and more people as the enemy, and stirring up others to fight against them. Rather than allow society to arrange itself naturally and have laws to stop discrimination against anyone, they go beyond making everyone be treated equally and try and reduce the chances of those they perceive to have an advantage. That is the same as shortening the legs of high jumpers and giving people drugs to reduce their intelligence to make them get similar exam results. Fearing difference between people is behind so many wars and discriminatory policies worldwide, being terrified the powerful will subsume the remainder so will do everything they can to reduce their power down to the average, including spreading false beliefs everyone is the same whatever their background, race and intelligence, which they all claim are only produced by their environment besides science proving they are not.
So clever children can no longer be sent to different schools (unless people pay, which discriminates against the poor majority who cannot afford it), police are criticised for criminal profiling, despite the fact large amounts of crime are carried out by organised gangs from a single cultural group, and everyone everywhere is condemned for pointing out the obvious like very few non-Muslims are currently terrorist bombers. It reaches full circle now, with the accusations from the left whenever someone associates a crime with the fact the perpetrator was a Muslim they are Islamophobic, when many Muslim countries (as well as individuals, as it is taught in the koran) discriminate against homosexuals, as they simply can't support both. The old primitive view 'The enemy of my enemy is my friend' can never work in the end, so while they defend Islam to the hilt, protecting their rights and culture even when they were not called upon to defend it as non-Muslims, their total commitment to equality (read 'homogeneity') means they cannot tolerate any negativity aimed at homosexuality, which creates quite a problem where some of the most genuinely homophobic people on the planet are indeed Muslims. I don't care how they try and resolve the problem as frankly such outcomes become inevitable when a group who view all cultures as equal, and they should all live together, and do not have a solution as they are based on a false foundation.
Besides the odd banana skin the general weight of such views does nothing but create a society of small and large groups who all feel persecuted by the others, and do not believe they can succeed under their own individual merits so must stop the competition and bring them down to size otherwise society will not be 'fair'. They cannot see that strangling everyone's individual potential by claiming they are the same whether male, female, disabled or whatever, when in fact although every life is equal and every person must be treated equally, each individual is unique and ultimately responsible for their own fate in life. You do not fail once and give up, you have endless chances to try again and differently, and if you blame others for your failure that is the only true failure to every type of success.