Without knowing more, I'd say you've done the right thing.
That said -- and hear me out, in the spirit of 'believing in the power of rehabilitation' -- how long ago was the sexual assault, and how old was he? A co-worker has an 'underage/statutory rape' conviction from before the 'Romeo and Juliet'-laws, because he was an 18-year-old (legally an adult) dating his 17-year-old classmate who had exceedingly posessive parents. (Also, he's a gentleman of color, and she was white -- and I'm sure that plays into the situation). Even though this took place nearly 30 years ago, he's still considered a 'sex offender' and carries all the legal and social stigma that comes with it.
You say he's significantly younger than you -- and that the assault was also a while ago. I'm not justifying crime or assault by any means, but I think a carved-out exception for the situation I describe could be a possibility. Of course, if that's not the case -- then, *whew!* you dodged a bullet.