that's not really censorship though. i have no problem with that.
Why is it not censorship? Obviously it can't be in the legal (1st Amendment)sense because Facebook is not government run, but the accusation is that, within its own medium, Facebook is intentionally making it so certain political content does not appear in favor of other political content.
Another accusation was Google modifying its suggested searches to include only positive suggestions for Hillary-related searches (i.e., autocomplete would not fill in any scandal related terms even though they were far more searched) but include negative ones for other candidates.
I don't think anyone is claiming any of this is illegal, but if true it certainly should weigh on the credibility of the companies.