The world is rich and varied, and we have our perception to recognize and appreciate that, eventually learning how to enjoy being a part of it. We can be a part of it by also being rich and varied, open people with broad outlook who're not afraid of discovering more of the world, like children.
Somehow keeping this interest for discovery alive as we grow up may be a hard thing to do. But if we let it die, things tend to only get worse over time, at least the way we perceive them.
Amusingly, interest is like a muscle: the more you look for ways to use it, the more powerful and useful it becomes. The less you care about it, the more you miss out on its results, usually without realizing.
There are certain feelings that tend to limit our perspective under various nominal excuses, and sometimes they are as insistent as some kind of a hallucination, so it's easy to learn to give in. What usually happens next is enough people agree to limit their outlook and perspective, to become more average, and that eventually lowers the demand for crazier people to hold back. Being average becomes a norm, nominal excuses become critical taboos, helpful standards degrade along with the overall mood of the society, and if all that continues, the entire civilization risks falling into a long-term crisis. Because everyone limiting their perspective means the society atomizes itself and basically decays.
The fewer factors you look to consider in any given problem, the more you fall into the trend of black-and-white, binary thinking, and the more you depend on nominal pathos of how it all looks, losing touch with reality and things that actually define reality. Which is, conversely, not a nominal problem at all: it's a path into psychosis. After that, the only thing that matters would be something that drives you crazy that you can't fix for real, going only more crazy. Part of the problem is weird methods you start believing in, and other people disliking those methods somehow starts looking like a proof the methods are brilliant. Only because your impression of those methods seems to perfectly resolve the only problem you care about (in theory).
That's when entire groups of people can get really brutal, causing damage that escalates or even creates the problem they're fighting in the first place. Like a self-fulfilling prophecy, which is usually pessimistic about other people and optimistic about the group that believes it. At some point people start believing that brutality has a magic ability to fix other people's misconceptions without creating the new ones (that are potentially worse).
If someone thinks that having enemies that hate your guts is absolutely normal, they get stuck in questionable practices that only multiply their enemies. You can't limit your care about other people's opinions only to the people you like. Because if you disregard your opponents' opinions as invalid just because they're seemingly against you, you're essentially dehumanizing them while being narcissistic, attributing them bad faith of being personally against you no matter what. If hating your guts is normal, then you contradict yourself by considering negativity a norm: if being bad is normal, then what is actually bad now?
None of this makes current life more interesting and enjoyable. Even if people think they'll be happy after their revenge succeeds, that's still expecting to become happy in the future (potentially), rather than learning to be happy right now. Or they keep poking at a sore that reminds them of a catastrophic past that they can't undo, which also means they're locked out of the current moment and its live context (and opportunities).
Good thing is that being happy is natural, if we only learn to refrain from the bad trends. And naturally, if group aggression is what we want to avoid, then we need to recognize in ourselves feelings that are aggressive. No matter what the nominal pathos of a feeling is, if it pushes its agenda aggressively, then it's destructive in its nature.
It's a counter-intuitive trait of destructive practices: they declare a goal that has absolute importance, and then they start sacrificing people for it, even if that method directly contradicts the goal. Absolute priority they assign to a nominal goal is just a red herring for the methods they want to practice at any cost. If you prove them their methods contradict their goals, they either ignore it or switch to another nominal goal of absolute importance, just to make their methods look like the only option left. Their actual goal is just practicing their brutal methods indefinitely. See how that goal is impossible to reach once and then calm down, switching to something else. It's an obsession that has to continue so bad that it's ready to create problems just to keep fighting them, brutally.
Aggression being a trend means the society can fight it by cutting it short, first in yourself, and only then in other people. But it's also critical to constantly come up with solutions that don't involve aggression and are also more practical, because aggressive people can't simply stop being aggressive, the only thing they can do is switching to something that is smarter and more helpful. Essentially, they need to understand that aggression is absolutely not their last hope and only option. And that can take years, but with due diligence it changes people.
We're almost never in a final fight against absolute evil that is outside us, so we better use the time we have until then, to properly prepare - by fixing all the relative evil that is inside us. We're not in a deadly race, and even if we were, paying attention to details is how we win, not through rushing our decisions. And once we learn to be patient and mindful, we'll discover infinity of options that don't involve aggression of any kind, and tons of reasons to be happy! Only on that path we may find out that some problems are really only fixed by being strict and strong, but still only if we're strict and strong towards ourselves first and foremost.
All in all, being open and interested is not just a nice advice, but a practical tool to succeed as a civilization. And the risk coming from the opposite is not a blindly feared taboo, but catastrophic trends leading to wars and long-term conflicts. Don't trust feelings or impulses that lack explainable foundation and an uplifting goal, and you'll start creating reality that's not limited or limiting.