But you could apply your theory to today: what is it that triggers most conflicts today? It seems to be it's most ideology. The West is highly ideological (like everyone else, it must be said) while not acknowledging it.
Could you "be friends" with authoritarian countries led by dictators? If not, why?
Many countries' populations appear to see authoritarian regimes as the preferred way to govern, from China to Iran, Russia to parts of Southern and Eastern Europe. You can claim most people would prefer something else but are silenced, but I don't agree with that, as countries "forced" to be democratic, like Afghanistan and Iraq, unequivocably go back to being authoritarian as soon as the "oppressors" leave.
It's official policy of the USA to spread democracy: https://en.wikipedia.org/wiki/Democracy_promotion_by_the_Uni...
If you're the ruler of a non-democratic country, you would take this kind of behaviour as kindly as the USA would take any other country trying to spread authoritarianism, wouldn't you?
Whether one ideological belief system is more correct than another, or more just, is kind of beyond the point (and very difficult to prove objectively anyway)... my point is that if you're willing to accept a variety of cultures, ideologies and so on, you must not lay judgement at all on others, and specially you must not attempt to crusade around the world trying to impart your own believes on others. Accepting that would go a long way towards "everyone being friends enjoying the differences".