Totally agree, and thanks for sharing - I hadn't heard of that correspondence, but it was worth reading.

In Freud's letter, he says that if we want a "durable union" between people, we'd ideally have "a community where every man subordinated his instinctive life to the dictates of reason."

I agree with that, and wrote an article about how we need a universal "religion" to accomplish that: https://medium.com/@nebulasaurus/will-humans-ever-settle-on-one-religion-4e50c81b1d96

I also come to a very similar conclusion about violence, under the heading, "Violence is Always an Option".