While I agree that categorization is a definitely human construct, I think that the process of conflict involves far more, including biology and the laws of physics themselves.
Let me explain. And while I don't want to turn this into a political discussion [mod hat]note we have a "no modern politics policy in the forum[/mod hat], I'm under impression that humans have evolved with a" tribal gene" in place. Look at us now. We are grouping in this forum as Steampunks. We are grouping in this thread as LGBQT+ or Queers. We are grouping ourselves in this forum as makers, amateur historians, sci-fi writers, etc. You name it. Rule 34 for socialization (instead of porn)

but clearly a human construct. We separate ourselves by our common interests.
The racism, homophobia, xenophobia, etc. is nothing but a consequence of the long term isolation of racial and social groups groups which leads to relatively superficial differences in our anatomy and behaviour. Yet the tribalism in our society can take a turn for the ugly really quickly when we dehumanise the other group. "Our people listen to this music.. What music do YOUR people listen to? Because obviously your people are not the same as MY people." You have no idea how many times I have been asked that question. You see where this goes:
"I was perfectly alright when YOUR people were NOT here. I noticed that my life is not as good now as it was xxxx years ago, and I noticed that my bad luck started after YOUR people arrived. Therefore it is YOUR people's fault that I'm having trouble. I want to go back to the past when YOUR people were not here. That will surely make things better. The past was better, let's go back to the xxxx year, to the YY century or even the Z millenium back when things were all-right."
This is very much a tribal mentality, and you have to learn to see the other people as fundamentally different to you if you want to cleanse your group from the influence of the" others." You can see this process of dehumanization all over the world in the news today. Literally, we are living in an era of extreme nationalism all over the globe. The 21st. Century has turned out to be a great disappointment in that sense. The only thing standing in the way of xenophobia, is the characteristic "inclusivity" factor of a society. Itself another cultural construct.
A society's inclusivity can be measured by how similar people in the group think an outsider is to them. Compared to Latin America, for example, the United States has a really low inclusivity factor. Even though we have people from all over the world, we still tend separate into groups largely based on colour of skin, which I would characterize as an "American Obsession."
In contrast, racial mixing is the De Facto mode in Latin America. After the Spanish mixed in with the Native, after Latin American countries became independent in the 1810s, waves of French, Italian, and even German migrants came into Latin America (not just the United States - often a fact unknown to the American people as others in Europe). What do you think these immigrant groups did? Separate? Well initially to an extent they did. But on average by the 1890s it would only take 1 or 2 generations before these non-Hispanic Europeans started mixing into the population. Why? Even I as a half Mexican have French, Italian, Basque great grandparents, on the Mexican side alone, not to mention that I'm half American of English and Dutch descent. Yet people in the US will "pull the colour" out of me and ask me, "What music do YOUR people listen to"? Geeze I don't know..." So I feel like answering, "Normally I rip the skull off a goat and use it as a drum in preparation for ritual human sacrifice. You know, it's an Aztec thing."

So what to do about it? The problem is I don't know how other than education. Literally undoing the tribal propaganda of political leaders. What must be true is that going to the past is not the answer for those tribal groups. There is something called Entropy which is a fundamental characteristic of the universe (linked to the fact that time only flows forward). Entropy is defined as a state of disorder. Look around you. Wherever there is a major conflict and abuse of one group over the other you usually find the same argument at the centre of the conflict :
"I was perfectly alright when YOUR people were NOT here. I noticed that my life is not as good now as it was xxxx years ago/ YY centuries ago, and I noticed that my bad luck started after YOUR people arrived. Therefore it is YOUR people's fault that I'm having trouble now. I want to go back to the past when YOUR people were not here. That will surely make things better. The past was better, let's go back to the xxxx year, to the YY century or even the Z millenium back when things were all-right."
Look at the worst offenders around the world. The argument is exactly the same regardless of their colour of skin, religion, nationality, you name it. We have now large swathes of people around the world wanting to go back to the past. In any continent you look at. They want to go back as far as 5000 years ago, or as recent as 60 years ago, because "those were the good times." An infantile illusion forwarded by the tribal mentality, which may be an evolutionary trait of primates. But when they try to make society go back, all they accomplish is to create intolerance, violence and destruction. That is the very definition of entropy. The penalty mother nature makes you pay for trying to reverse the time arrow.