I think it would probably not be best to remove the propaganda posts in question, but would probably be good to perhaps have warnings applied to posts linking readers to authoritative sources of information about the subject, so the readers can make their own unbiased judgments.
Freedom, or no freedom? There's no grey area here. Should people be able to say what they want on this forum, or should all posts be reviewed against QS's definition of propaganda? Who gets to review the "Authoritative Sources" to determine whether if they valid, or if they are just spreading more propaganda? Who gets to review the reviewers for bias?
My suggestion is that you engage in calm, rational discussions, provide references that support you position, recognize that your opinions are just as biased as your opponents, and allow others the same freedom. You won't convince everyone. You may not convince anyone. Just don't take it personally.