Phil Collins has true talent he can write about anything! Some artists just write about love! Or typical lyrics like the songs where you can tell what word is going to be next! Annoys the hell out of me.
This song has truth and meaning of how "things look different behind closed doors", so don't be to quick to judge a book by its cover without listing.
He means by saying Both side's of the story is that our judgment on people always seems to come first, and that their side never gets heard. Phil is saying sit down and listen maybe then you will see we can have a bit more understanding and truth of the world.
Don't you hate it when someone you hardly know judges you, yet they have no knowledge of whats happened in your life, and whats made you do something that seems wrong to other people? And whats worse is they haven't heard your side of the story!