I think what you're not addressing though, is that often the work engineers are doing is political. No one can doubt that Facebook has fundamentally changed politics, no one can doubt that the way they set it up had spectacular effects on politics in this country - and that they're now deliberately modifying their system to have a specific political impact. Maybe if they'd thought about the politics of their system as part of their design stage, they would've thought about what damage they were going to cause. The choice not to has arguably been a massive blow to democracy.
Say a conservative becomes CEO of AT&T. Should they consider the "damage" that will be caused by routing calls for liberals, embrace their political responsibilities, and kick suspected left-wingers off the PSTN?
Republicans are real people who really make up approximately half the voters in this country. The "threat to democracy" here is the suggestion that it's a moral imperative to rig core communications infrastructure against them.
Facebook hasn't "fundamentally changed" anything. Right wingers just happened to be savvier at manipulating the tools it provides, this time around. If anything, that's a surprise. One would expect social media to be good at rallying younger, tech-savvier, more left-leaning voters. One would expect the DNC to run the savviest social-media campaign, based on its track record in '08 and '12.
