Based on psychological research we know that early childhood trauma can help develop sociopathy. It's easy to see the effect of perpetual violence in terrorist hotspots like Palestine where children grow up to become terrorists because of the violence they experience in "counter-terrorism", which their existence as terrorists of course feeds into, repeating the cycle. As the saying goes "hurt people hurt people".
I think it's a mistake to look at a civilisation past or present that is defined by widespread violence and death and think of it as anything other than dysfunctional. It's just that the baseline of suffering is so high it drowns out all the easily identifiable forms of suffering we're accustomed to.
You often hear people talk about the cultural trauma of Japan, Russia, or Germany. As an outsider there's also a clear circle of violence in American society which pervades and informs cultural attitudes, social policy and conflict resolution. This shouldn't be surprising given the US's history of widespread suffering throughout its history: indentured servitude, religious prosecution, chattel slavery, genocide, disease, civil war. American hyperindividualism as well as both the Cold War and War on Terror "world police" eras of foreign policy and the more recent popularity of isolationism have all the trappings of a trauma response.
Meat is violence. This is why slaughter is often highly ritualized in "primitive" societies, often thanking the animal for its part and being deeply aware of the interplay of life and death that meat eating requires but also the importance of the slaughter for the survival of that society. Both the meat-eating urbanite having an existential crisis over having to kill an animal for sustenance as well as the farm hand thoughtlessly killing an animal are in unhealthy positions - one from the detachment of mass production, the other from the desensitization of their involvement in it. The vegan might be in a healthier space but given modern industrial production is likely as detached from the food they consume and the suffering and death that enables it (be it the field hands working in bad conditions for low pay, the animals dying in the process of industrial farming or the ecological damage caused by shipping exotic or out-of-season produce around the globe).
I say that as a city dwelling meat eater living in Germany, which is a deeply unwell country scared of understanding its own history beyond easy platitudes and simple stories of good and evil people. Humans are not a virus but humanity is very sick and it will take a long time and a lot of effort for it to get any better - if ever.
More to the point: as someone who has had a justified need for therapy before, I think it's important to recognize that of course you can often simply "push through it" because if you can't, you simply break. But importantly you won't get any better, you will just appear more functional for as long as you can keep it up. Therapy was a taboo in my lifetime and I'm not even 40. Suicide is still often a taboo but only started being acknowledged a few short decades ago because a number of celebrity deaths became widely publicized (in Germany it was a soccer player, the stoic masculinity equivalent of an American quarterback). That didn't mean these things didn't happen before. It just meant we didn't acknowledge they did and we didn't know how to get help.