I'm no fan of Facebook, but I don't get why they're to blame for Russia's meddling in the election. It's hard to believe that they were aware of what was going on and allowed it to continue because they were making money off of it. The money they were getting was a pittance, all things considered.
So people are angry that a media engine was used as a platform to deliver content designed to sway their opinions and behaviors using various forms of mendacity, exaggeration, obfuscation, prevarication, suggestion, dark psychology, titillation, and propaganda. Doesn't that describe all advertising? Also, shouldn't we be slightly happy that US tech companies were able to export US-audience advertising capacity to Rus…
Second potential problem is that it is alleged that Facebook employees were embedded in the Trump campaign's digital efforts. This would not necessarily be a problem in and off itself, but there is a lot of rumbling about stolen voter data that was used for microtargetting on Facebook. If Facebook had knowledge of data that was illegally obtained by a hostile foreign intelligence service, there could be some additional culpability.