I wouldn't vote for Barr even if the Libertarian party had a chance in hell. From what I've read of the guy, he's NOT a Libertarian.
A dozen years ago you'd have been absolutely right. Just for starters, Barr was a major "drug warrior" (ban it all) type and a big-government supporter to a lesser degree.
What happened was, he looked at the civil rights violations post-9/11 and realized that ALL of the garbage had it's origins with the "War On [some] Drugs"...and did a major ideology shift on a "Paul on the road to Damascus" scale...
He really is Libertarian these days.