I think the hard thing to understand is that all people, including guys, are a mixed bag. Every person has good instincts and bad ones. You want to spend your time with those who more often follows his/her/their good instincts.
That said, as a guy, I believe (sadly) that way too many guys follow their bad instincts. This is really really unfortunate and I hope that I'm wrong about this.
I'm happily married and getting old. I might have been one of the (more often than not) good guys. But I'm no prize either. I can be dull. Or thoughtless. Or lost in my own head.
But I am rarely cruel. And, if asked, I am usually generous. Over time, I'd like to think I've been getting better.
I don't know why people can be so selfish—it seems incredibly foolish to me. I mean, we all share a common humanity. Life is short and challenging. Can't we TRY to be there for each other? Even if, sometimes, we fall short?