Hackernews is living proof. Pre-election, you could voice a contrary opinion here and have a discussion. Post-election, even the faintest wrongthink shibboleth gets silently downvoted into oblivion.
When I see complaints like this I always look at the history. Usually the account in question has a pattern of posting flamebait and/or snark. In that case you needn't reach for political bias or 'wrongthink' to explain why the community downvotes such comments. They get downvoted simply because they break the site rules.
That, and wrongthink need not limit itself to politics. On HN we have it for technologies as well!