Jaw dropping start of a "Just Say No" discussion

Prompted by something he saw on television last night, my soon to be 11 year old said that he thinks marijuana should be legalized. Within a few seconds, a hundred thoughts were going through my head. I have learned that a shocked, jaw dropping response on my part creates discomfort for him and inhibits open communication for our future. So keeping in mind that I want my son to be able to talk to me about anything, I quickly maintained my composure and asked "Why do you think that?" To which he replied "Because it helps people who are suffering from terminal illness." I was instantly reminded of a close friend of mine who I watched suffer through cancer that ultimately took her life. Smoking marijuana was the only thing that provided some relief from the pain and from the side effects of chemo. Do I tell my son about this? Do I tell a 10 year old that on some level I agree with him? I decide to ask more questions starting with, "What did they teach you about marijuana in DARE?" Lucky for me, my son just graduated from the DARE program a couple of months ago. He proceeded to tell me everything he learned including that marijuana could be a gateway drug and lead to the experimentation with stronger drugs like cocaine and heroin. I felt a little sick to my stomach when considering my son's curiosity and how it won't be long before he is a teenager and has to make the choice to say no. At least I hope with all my heart that he chooses to say no. I tried really hard to listen to him and wait for the right moment to put my two cents in. I felt proud of him as he spoke. He said, "Alcohol is legal and I think it could be like one of the worst drugs out there. It's legal but like, it doesn't help anyone who is sick like marijuana does. It kinda doesn't make sense Mom. And the DARE teacher told us that like one of the biggest addictions in America is prescription pills." Wow. I am impressed with the DARE program. As he talked I decided to take this wonderful opportunity to provide some of my own feelings on the subject of drug use. I told my son that the day would come when he would have to make a choice. We talked about peer pressure and curiosity. I told him what my expectations were and that I understand how hard it is to be kid sometimes. I assured him that I am a good listener and even though I'm his mom, I will listen without judgment when he wants to talk about the pressures of growing up. We talked about the dangers of drug use and I told him my sincere hope is that he won't try marijuana no matter how strong the temptation may be. Right now, he assures me with a promise to say no to drugs. I told him I think he is wise beyond his years and that I was confident he would make good choices in his life. At the end of the conversation I felt confident enough in my son's understanding to tell him the story of my friend. My friend with cancer who used marijuana to ease her pain. Ultimately, I didn't feel comfortable enough to agree or disagree with a 10 year old and his position on the subject of legalizing marijuana, but I did let him know that his opinions were valuable.