By rebroadcasting what is available on air for free, the stations will assert the online shows are stealing away their advertising dollars as each person that moves to online viewing will not be seeing the ads that are shown on onair broadcasts and thus these advertisers will pay less as their audience is shrinking.  Similar to magazines on how they charge for advertising based on subscriptions paid versus online reading advertisers pay for each person that accesses and another charge for those that click through and actually read the full ad.