I was wandering about in a craft store last night just before it closed, trying to find a circular knitting needle, when I heard a couple talking a few feet away, and he responded to a quiet remark of hers by saying hotly, "Why the hell should I practise tolerance, let him do the practising for once, miserable old bastard!"
In Al-Anon, in any 12-Step group, it's suggested that we
Let It Begin With Me.
Many of my new sponsees have said in reaction to that high-minded idea, "Why should I?"
I give them the answer my first sponsor gave to me - because you'll feel better. Since you have absolutely no control over how another person behaves, why not work on the one person you can change - yourself.
Put simply, tolerance feels better than judgement.