Jewish background for the mansions theme:
Back in the day, when a Jewish man wanted to marry a Jewish woman, he'd get "engaged" - which was an engagement so strong it actually required a divorce to break - then go and start building a house. This "house" was basically addition to his father's home, and over time they became very large, sprawling complexes where the family and relatives all resided. When the man's father deemed it was good enough, the man would grab his friends and run off to meet the woman. She had to be ready and waiting because she didn't know when he'd be coming, and it was a kind of fun surprise. He'd get her, they'd go on the honeymoon, and then live in the family complex. (No, I don't know much about Jewish marriage or honeymoon.)
Jesus said, "in my Father's house are
many mansions. If it were not so I would have told you."
With that background, Jesus was not only saying "hey, there's room for everybody here!" (which the Jews would have interpreted as room for all Jews). Jesus was also saying "there's room for
everybody. Not just Jews, but Samaritans, Romans, Persians, Greeks,
everyone! Quit judging!"
I'll let mayflow take over the explanation now.
EDIT: Merrytrees, you're bang on. Churchianity talks about love and compassion, but doesn't live it. I will point out, though, that there are many Christians who do actually love and have compassion. But you're right that Religion isn't doing a very good job of teaching love...