There's nothing you can do if someone is dead set against rushing.
If he is willing to keep an open mind... try inviting him to some all-greek things like Greek Week... my school had a Greek Week formal every year, and you certainly didn't have to be affiliated to go. Get him to go to a fraternity or sorority charity fundraiser or two. If you have other friends who are in fraternities, introduce them. Show him there's more to greek life than keggers.
If all else fails, remind him that the fraternities will feed him during rush, so he won't have to worry about food for 3 days or so.
