No, you're thinking of /r/conservative, which literally has "flaired users only" posts, and insta-bans people who express even mild criticism of conservative talking points.
"Do not violate the Mission Statement. (We provide a place on Reddit for conservatives, both fiscal and social, to read and discuss political and cultural issues from a distinctly conservative point of view.)"
And when you suffer from constant brigading, this is a reasonable way to deal with it. If /r/liberal did this, fine. /r/politics belies its name by being a liberal echo chamber. And _yes_ you can easily get banned there for expressing perfectly benign, but unpopular views.
"Do not violate the Mission Statement. (We provide a place on Reddit for conservatives, both fiscal and social, to read and discuss political and cultural issues from a distinctly conservative point of view.)"