The legalization of marijuana would do nothing to the hemp market as hemp and marijuana are two different things and one is legal while one is legal and the other is a category one drug
Weed is far less harmful than any other drug as most other drugs can lead to death from the drug itself while marijuana has not been linked to many if not any deaths at all
There is no link between the use of marijuana and heavier drugs, the more common gateway drug which actually has been linked could be something along the lines of ecstasy or Xanax
The medical use of marijuana is outstanding and people try to argue that is has many bad affects on the body, but many people still drink and smoke which both are completely legal and do far more harm to your body than marijuana could ever do