The Washington Post published an article that indicates that some of the defective genes found in those with autism may be used to promote learned behaviors as these particular genes are developed through interaction with the environment. While this doesn't offer a cure for autism, it can be quite useful in behavior modification techniques.
Many parents of those with autism will not place their autistic child in situations that are uncomfortable for them. However, at some point this child is going to have to deal with the world, which is not going to modify itself for those with autism. Not to mention the fact that no child or human being learns anything by living in complete safety with respect to avoiding new experiences. Though it is entirely plausible that new experiences be approached with caution and at a pace that indicates "baby steps", they CAN still be approached.
The use of mental activity to stimulate genes that will help in behavior modification is a very simple concept that only requires practice and interaction with the world. For instance, if the child who has autism is high functioning enough to have no speech barriers, yet they appear rude to you and others, practice manners with them. Do not excuse the behavior for them, because the rest of the world isn't going to. Simply practice with them. This can be done using role playing, story boards and discussions.
In short, those with autism simply need to work the muscles that are the hardest for them to work. It really is very basic, yet it is a concept that some parents avoid in order to "protect" the child. In the end, avoiding new situations and mental activities that are not entirely comfortable may be doing the autistic child more harm that good.