Is your entire paper about how legalization can benefit autistic people? Or is that just one of your points? Well your intro should just summarize your main points. If it were me, and I have done this exact topic before a few times, and even been paid for it a couple of those times, I would come up with like 5-6 main points that make up the body, then write those out. The thing about austism would make a good point for your body, it's a good start, but I wouldn't use that for your intro.Your intro and conclusion really should be the last things you write, as they just summarize your entire essay."Marijuana is highly controversial and there are very divided opinions on its usage." is a good statement to put somewhere in your intro. Don't focus on the intro or conclusion till the rest of it is done, otherwise you'll be stuck on it, because it's always gonna keep changing.