Our society does do that on TV and radio. Consider the recent boycott attempts against Laura Ingraham: https://en.wikipedia.org/wiki/Boycott_in_support_of_David_Ho...
>Do we assume that if you're ad runs during <some sitcom> you agree with the jokes in it?
I don't think most people actually assume that the advertiser literally agrees with all the content they are running ads on. Rather, I think that people have found that it's an effective ideological weapon.
Going after the advertisers to attack content is a tactic that works. The attackers don't have to literally think that the advertisers are morally signing on with the content, they just have to think that enough people out there think that, and that the advertisers are risk-averse to bend the knee, that it's a useful tactic.