I think there's a difference between dirty versus bad tactics. Many bad tactics I've seen are from strong riders coming in from other athletic fields where fitness is the only thing that matters. They don't realize that bike-racing is +95% strategy and mental tactics.

So this guy I know demolishes the beginning fields by simply time-trialing off the front. Gets up to cat-3 in just 2-months and tries the same strategy... HAH! He does lap after lap pulling the entire field around behind him. At the finish, they all just blow by him like he's standing still....