I really don't want to escalate this argument, but I feel the need to change a little of Yamato's statement:
LDS people do not believe in all of the "If you are not good/do a bad sin, whatever, you will have a horrible afterlife, etc", in fact, we believe that to get a place like that, you would have had to (IIRC, may not be 100% accurate, correct me if it's not) have known Christ to be the son of god or known god exists without a doubt and rejected him. Only a handful of people would actually fit that description. We believe that there are three levels of glory you can obtain:
Celestial kingdom: Highest level of glory. Needed to be baptized/under 8 (those under 8 are not accountable for their sins yet), be really good in this life, repented, tried your best, etc.
Terrestial kingdom: Second degree of glory. In general being a good person and whatnot. Many gay marriages, atheists, and others who have stances against what the LDS church believes may end up here (if they are good people).
Telestial kingdom: Last degree of glory. Those who were bad/didn't care/whatever other reason go here. It is 10X better than Earth.
We also believe that before the judgement there will be a time for those who did not have a chance to get the gospel in life may be taught it and receive it if they choose. This part I don't know exactly how it works (I mean, if there was only one church teaching wouldn't someone catch on to it? I just don't know.)
Anyway, we are far from condemning those to a horrible afterlife if they don't believe, just as we don't say everyone who believes is in an amazing state. It depends on the kind of person you are and how you act.
Anyway, I didn't mean for that to become a text wall. If this isn't your opinion, I am really sorry, I misunderstood.
So, continue.