The original word here is Gehinnom and in Jewish thought carries a different meaning than the Greek word Hades which is also translated as the word Hell.
In Jewish thought, what you do is as important as what you think. In other words, if you don't have the self control to stop doing what your doing, then cut it off so you can't do it anymore. If anything, Jesus is warning us of our behavior and is stressing that what we do is indeed very much a part of our salvation.
As Christians, I fear that somehow we've strayed from the core of Christianity and it's almost taboo to tell somebody that they are not living in accordance with God's word. We are so fearful of being doctrinaly correct that salvation comes by faith, and faith alone we have lost the importance of what Jesus was teaching almost to the point where how we act and what we do is secondary to what we believe.
The problem with this thought is exactly what James counters by, "I will show you my faith by what I do" which is never a popular passage to quote... But we should at least try to live as God wants us to live. It's the "least" we can do.
