Beats the hell out of me what the problem is. Maybe they consider it a diminutive form, and so it's racist because you're calling him by his "boyhood" nickname? I've known two males whose real, full, given name was Barry. Barack is an un-Anglo, unusual, awkward name anyway. Perhaps they're concerned he lacks the head-of-state gravitas, so everyone needs to toe the line and pull their forelocks?
I frankly think it's disrespectful on some level to call any presidential candidate by their given name, just like the unmannered idiots who call me on my home phone and presume to address me by mine-like I'm going to be warmed rather than offended by the unauthorized familiarity.
What should we call them then?
I think the DUmmies are just looking for reasons to hate conservatives.
You're right, of course. As for your question, my opinion was that keeping it to Senator ________, or just Obama and Clinton would be sufficient to stay out of trouble. And if the candidate wasn't a current holder of office, then Mr. or Ms. or Dr. or whatever, just like in other formal address.
