Now this is interesting. As a commenter mentioned, Bob Barr was accused of yelling racial slurs at a security guard a few years back. Usually those sorts of accusations will get you accused of being racist. But when you're in my cross-hairs and you've got the visage of Bob Barr, they get you accused of being black. It isn't just that accusation, it's also the fact that Barr apparently gets really pissed-off when people ask him that he's black. Who'd get mad about that? People in NY start speaking Spanish to me all the time, apparently thinking I'm Puerto-Rican. I wouldn't get pissed...unless....
I tell you a smell a conspiracy. It's really coincidental that Bob Barr will be taking votes from McCain, thus helping us elect a black man. Isn't that kinda funny?
The Beautiful Struggle: A Father, Two Sons, and an Unlikely Road to Manhood 
Or they think your from the DR. Puerto Ricans are not the only dark skinned Spanish speakers.
If I got mad every time someone thought I was a different race, I would spend all my time mad about being asked if I'm black, Latino, Arab, Persian, Italian, Jewish, Greek, Spanish, (once) Chinese(?) and (once) an Afrikanner(?).
I was just talking today with a friend/colleague who used to work for a since-deceased member of the Congressional Black Caucus back in the '90s. Evidently, the office (along with all CBC offices, presumably) received some sort of anonymous letter telling them they should consider Bob Barr for membership in the CBC.
Maybe you're on to something with this guy, although I don't no him. I have a coworker who is latina and somewhat ashamed of it. She hates strangers speaking spanish to her in public.
I could be wrong, but is the incident in which you are referring to the same as the one detailed the New York Times article from 1998 (part of which is posted below):
"Representative Bob Barr complained that he had a plane to catch, but the young female security guard at the airport metal detector cursed and instructed her colleague to take her time looking through his bag. When Mr. Barr angrily demanded her name, she stuck her ID in his face, and he slapped her arms down forcefully. She came charging back at him, and he yelled, ''Nobody swears at me!'' The guards who quickly surrounded them led her away, and he walked on."
If this is the incident in which you are referring, it would seem that it was the security guard that swore at Bob Barr, not the other way around. Somewhat irrelevant to your conspiracy theory I suppose, but still...
*the entire article titled "The Georgia Republican Who Uses the I-Word" can be viewed at http://query.nytimes.com/gst/fullpage.html?res=9801E1DD1131F93AA35756C0A96E958260&scp=3&sq=bob%20barr%20uses%20I%20word&st=cse
My bad...did a little more looking and found an article on what you are referring to. Not the same event.