Social media sites are generally perceived as "common carriers" whom we expect no political activism from (beyond refusing illegal activity & promotion thereof) - to wit commercial entities whom we expect will not lobby (legislators nor customers) re: non-sequitur topics.

Well, we expect social media sites to try and avoid blatantly taking sides. But they definitely thrive on human-interest stuff (such as this), especially if it's something with a social mobilisation aspect, and that's almost bound to skirt the political rather closely. As it does here. At best you might expect social media firms to give opposing sides equal opportunities (even more business!). But even openly biased media is common - e.g. Fox news, but really many other news outlets too - and I see no reason to think social media firms couldn't evolve in the same direction.

I'm not saying we should applaud this development...

In any case, I don't see no evidence that snapchat it being particularly biased based on one story they're pushing. It's pretty much impossible to make that conclusion based on one story, given that they push so many. It looks more like sheer incompetence to me than anything else.

The other employees in his business were donating the services of the business to their pet political causes. Saliterman was trying to make money for the shareholders. It's an advertising business: that means everyone pays.

If Snapchat's board are all in agreement that that's where they want the money to go, fine --- but they should also realize that Snapchat is a social network, and the appearance of fairness is probably a reasonable thing to aim at. If the DNC or RNC launched a social network, they would find themselves somewhat hampered in their ability to grow, and with good reason.