Would they be able to stop people from doing it personally? Tweeting, emailing, actually telling people why we need to vote for the better candidate even if they are not the perfect candidate (Jesus has never been on a ballot).
I want to say no, but I know of many people who tried to post to FB during the 2012 election cycle and had their content blocked, or got blocked themselves. So, yes sometimes they seemed to do that. But, this is more subtle. Letting the "robots" nudge you, as Cass Sunstein would say..