NEW YORK -- "Did someone slip you a hash brownie?" So said Stephen Colbert, interrogating Libertarian presidential candidate Bob Barr, during the taping of tonight's "Colbert Report" on Comedy Center. The reference, of course, was to Barr's switch from a conservative stance on the war against drugs. One of Barr's key supporters in the Libertarian Party is the pro-legilization Marijuana Policy Project.