Here are some places to begin your response...
Second Largest US Physicians Group Endorses Medical Marijuana
Study Finds No Cancer-Marijuana Connection
As for cancer... Eat it, or vaporize it. Problem Solved.
Point out the double standards, compared against tobacco and alcohol.
Explain the history of racism and social control being the sole driving factors behind cannabis prohibition. Explain how you think it's time to end the racism
Finally, this bill really has nothing to do with marijuana, it is a bill to support State's Rights.
Replace marijuana with "killing & torturing squirrels for fun in the privacy of one's home" and it's still the same problem.
This is a bill to reduce the Federal Government's power, and to recognize state's rights for people to be able to use their
medicine(emphasize medicine, he's not a doctor, who is he to say what is and isn't a medicine?) that is legal in their State without fear of prosecution.
add your age, if you haven't already

show it's not just "teenagers and young people"
Start a petition, I'm in the process of writing one...
How to Write a Petition - wikiHow