If you had 20 minutes to present bitcoin to a room full of professional businesspersons, what would your MAIN POINT be? In otherwords, what would unify your entire talk?
Make the first 5 minutes a live demonstration. Show, don't tell!(Practice it beforehand to make sure it's smooth)
"Monkey see, monkey do" is one of the most powerful forces in marketing.
Also, use analogy. 99% of them will know how to use e-mail. 100% of them will know how to use cash. Probably 99% of them will not know how cash or e-mail actually work. So use familiar concepts to explain the unfamiliar idea of bitcoin.
Do not talk politics.
I think the most effective demo would be sending bitcoins from your laptop to your mobile phone.