Marijuana does no real damage to people; while some may not be able to handle themselves, to the effect of an addiction, the vast majority of people try marijuana with no ill effects. If people with terminal illnesses have had success with medical marijuana, there's no reason why people should stop them.
No, marijuana cannot help the terminally ill cope with their illness, because marijuana poses a number of risks and is still highly addictive. There are better ways to help the terminally ill cope and there are painkillers already in place to help individuals with terminal illnesses. Marijuana is also risky, because people who are not actually terminally ill will want to use marijuana, which will increase driving whie high traffic crashes and deaths.