The FDA should warn against dangerous drugs for sure, but they should make the case of what exactly is dangerous and why someone should not use it. With no other hope, parents should be allowed to determine what risk is appropriate for them and their situation. The FDA is not saying that this is a dangerous drug, they can't point to any failures at all , they are just saying they don't "think" SRPT is on the right track. But that doesn't mean it doesn't work nor that its dangerous. Just call it a "Beta" drug or something, parents can decide to opt in and assume all risk.
In this case, when there is no other drug, it should be up to the parents to try it. They are the ones living in the nightmare of this situation and if they decide to try an experimental drug, even if not approved by the FDA then so be it. For any drug that has no cure, the FDA should approve unless they absolutely have proof it causes more harm are makes them post idiotic rants on yahoo forums for reject requests to further their financial gain.