Earlier quoted context omitted.
Because cable companies pay broadcast companies to redistribute broadcast content - it's a major source of income for the broadcast companies. The cable companies said that if Aereo were allowed to get away with what they were doing then they'd do the same thing themselves.
OK, but do you understand that cable companies primarily provide cable channels as their service? You're comparing apples to oranges.
http://online.wsj.com/articles/SB100014241278873239815045781...