I would agree that this could be easily misunderstood, especially if someone is just glancing. I actually did not notice the medical part of medical marajuana until I read over it again. I guess glancing quickly I did not catch that word.
I would also think that you could write the essay about your passions and your activism without dwelling on the arrests. Yes you got arrested for your passions, and it may have been unfair, but it might resonate poorly with the ad com.
Individuality is great, talk about your passions, just stay away from the arrests.