Earlier quoted context omitted.
And /r/the_donald would say just the opposite. The thing about propaganda – why it works so well – is that it's presented as authentic civil discourse. There's no clear cut demarcation between the two types of speech. One could argue that /r/the_donald uses the banhammer to maintain order (the narrative), and /r/politics uses shill comments+downvoting to do the same.
What you just described sounds to me like an authoritarian court versus a democratic forum. That is, excepting the "shill" name-calling -- it leads me to believe that you are in fact speaking on behalf of r/the_donald. If that's true, then I know why the term was used. If not, what leads you to believe that anybody involved in discussion in r/politics are "shills".
Because Hillary had hired people to do exactly that:
http://www.latimes.com/politics/la-na-clinton-digital-trolli...
http://www.thedailybeast.com/hillary-pac-spends-dollar1-mill...
Remember someone leaked a private Slack chat of Reddit admins where one was boasting of receiving their CTR check.