If corporations are banned from trying to persuade people (i.e., advertising), they'll turn to bribing politicians (i.e. hiring lobbyists). Which is worse? I think that's clear.

I don't agree with Comcast's position here, but I think they should be allowed to be heard if they want to be. Democratic societies are strong because they're made up of a lot of strong non-governmental institutions and groups, not just an all-powerful government and powerless individuals.