The ideal gadfly is an equal-opportunity abuser, which makes A.C. Weinstein, political columnist for the Miami Beach weekly Sun Post, somewhat less than ideal. Example: He is slavishly devoted to Beach Mayor David Dermer and obsessed with undermining Dermer's political enemies. But that aside, his columns are as enjoyable to readers as they are vexing to the targets of his busy pen. As persistent as a hungry mosquito, Weinstein is quick to pull the rug out from under blustering politicians and haughty publications. He's also not above giving credit where it's due, even if it's the same person he skewered the previous week. Example: Miami Beach city manager Jorge Gonzalez. When he wants to, Weinstein can offer his readers provocative analysis of projects and policies that could have a real impact on their lives. But he seems happiest when he's the irritating gadfly relentlessly buzzing his victims.