Viscerally, I understand the reluctance. But we balk because of our skewed values. We feel like, if someone is "good" and kind, nice to kids and puppies, and merely doesn't happen to agree with us on this one doctrinal point... well, that's not worth his going to Hell over.
Basically, that's because we haven't worked out the implications of the First Commandment. Jesus says that the crucial commandment is to love the Lord your God with all your heart, soul, mind and strength; loving our neighbor comes second.
Saying that someone should get a pass on shattering the first commandment because he seems decent about the second shows we haven't fully embraced just how "first" the first commandment is. It is like saying, "Look, this guy pays his taxes, mows his lawn, feeds his dog. Just because he sexually molested that little girl — that's nothing to send him to jail over!" Well, yes it is. That crime "trumps" all the other virtues.
Or, to put it another way: here's a man with a loathesome, fatal disease. He'll take vitamins, he'll eat his vegetables, he'll subject himself to acupuncture. The only thing he refuses to do is to take the one medicine that will cure his fatal disease. Is it "unfair" that he dies?
Hope that helps. Go to my Message Board, get more answers and discussions.
Dan
Biblical Christianity web site
Biblical Christianity message board
Biblical Christianity BLOG
This may be a response more suited to discussion on the religion board but here goes. If God did not find other religions acceptable, why does He keep putting souls into babies that will be born and raised to worship Buddha or Vishnu?