Hundreds of years ago the earth being round would have been one of those not credible ideas that you would have suppressed.
As I read it, PP advocates for ignoring those people not suppressing them. Ignoring somebody and punishing them for what they publish is not the same.
Or perhaps more importantly, the question is who does the ignoring? The user or the platform?
Personally, I think users (and not platforms) need better to tools to selectively ignore. For example, it would be great if I could mark somebody on the social network as "unreliable source" and then all people parroting or use that source (transitively through the social graph) would be (proportionally) marked unreliable as well. And vice versa, why cannot I mark things that come from people I know personally as more reliable than things that come from some Russian troll farm (or - for the balance - American astroturfing startup)?
I don't know how you can spin undervaluing something automatically in an algorithm as anything but suppressing it. And it's not 'ignoring' if the person never seem them in the first place because they've been 'undervalued' in the ranking.
The big problem is that organizations like FB or Google want to "own" the social graph. They won't let you (except in special cases) to play with it.
Also, the idea that Western civilisation itself has gotten more scientific is both wishful, and imo would be a terrible thing if it did happen. We've just traded one appeal to authority (priests) for another (pop science promoters and journalists).
Materialism is a great way to investigate natural phenomena but I would hate to live in a society that treats it as a moral principle.