If the two of you have been good friends, then I'm assuming that friendship was built on communication and trust. So handing him a well rehearsed line that is cleaned up to spare his dignity will fail massively because he'll see what you're doing. I think if you truly value the friendship then you have to own it with the same honesty that the friendship was built on. But like all things in life, its how you say it that matters as much as what you actually say.

You need to tell him, " Hey I've been thinking about the other night and its really been weighing on me immensely. I feel it was a mistake to move this beyond friendship. I'm more comfortable with us being friends and do not desire the politics of a relationship which will change everything. I value what we have as friends and do not want to ruin that bond. I'm sorry I allowed this to move beyond that because it really wasn't my intention."

Now you might say that statement is candy coating it too. But to me, if you were really falling in love with this guy, the superficial things would get sorted in the process. I think your emotions might have just got the better of you, and in the final analysis its really friendship that defines the two of you. I really don't think the particulars you mentioned are the real players here. You didn't sign up for the Bachelors show expecting a stud. So to take this experience and narrow it down to superficial qualities as the real reasons is selling yourself short on the actual disconnect. His ultimate value to you is as a friend. So approach it from that perspective.