Friendship

I value friendship extremely highly and treasure my close friends. But then, every so often, somebody does something that leaves me slightly bewildered and most often disappointed. I treat people how I expect to be treated- with respect and honesty. So why can't other people behave like that? I set myself standards of behaviour that I also expect my friends to adhere to. Is that so wrong?
I recently found out that one of my closest friends had been behaving in a very under-handed, sneaky and downright childish way towards another person we both know. Now, they'd had a falling out some time previously, but I expected my friend to act with dignity and maturity. Is that really too much to ask? I dunno, as a result I feel I've lost both people as friends. Maybe they should consider who might be caught in the fall-out before acting so foolishly in future. But I doubt it.