The idea that some are condemned to an eternity in hell seems incompatible with the belief in a a God who loves all.
My Lutheran pastor has implied that everyone will go to heaven. He said that salvation comes through undeserved grace, and that not even believing in the wrong religion can keep a person from receiving that grace.
Jesus died for everyone's sins, didn't he?
That's not the issue though.
The problem isn't about God's grace, it's that Jesus himself said some things that are really hard to reconcile with universalism. I'm thinking of Matthew 25:31-46 in particular (the sheep and the goats). It's really hard (I'd say impossible) to square that passage with universalism.