We expect them to behave impeccably, but this is because hypocrisy is part of the human condition.  It's a subject that interests me because I've decided to make it the subjecty of a service I'm doing  a week on Sunday!  We want to find fault in those we look up to because it makes us feel better.  How much better must we be if we can criticise the highest in the land.
Likewise, have we ever done something for a friend, and it be nothing, until the friendship breaks up.  Then it becomes the biggest issue in the world, and they were the worlds biggest s***, and you even kept quiet about the time they ran the neighbours dog over....but no more.
When a relationship breaks down there is a lot of pain, amnd sometimes you want to dish that pain out.  After the breakup there are no bonds but those you choose.
I have a friend who is a driving instructor and he's had a few people taking speeding fines for him, because the ability to drive is important!