Because whataboutism: https://en.wikipedia.org/wiki/Whataboutism
What Obama did was unethical as far as I'm concerned, as is most modern marketing. (I will say one campaign was selling hope and progressive change while the other was fear mongering and spreading divisiveness. So I think there is a difference.) Having said that, I don't know that it matters. Granting these powers to people we happen to like doesn't mean they won't be abused by people we don't. Modern mass marketing is gross. It's the grand scale manipulation of people by exploiting individual human weakness/bias. I'd like to see some smart regulation around it, but I'm skeptical that will happen.