This might be favorite metaphor ever, and one I'll quoting in the future! :)
I think the author conflates social media with other inventions like a portable GPS device, an electronic map, a music player, or indeed a cell phone.
As far as social media goes the author is (IMHO) spot on. You do not have to look far to see how that is at least harming democracy around the globe. For democracy to flourish you need reflective voters who can entertain multiple viewpoints and make informed decisions. That is what social media - in its most common current form - discourages and rather optimizes for attention-time (which is money).
And of course (some) anonymity paired with global reach would not bring out the best in people. Anger and flames spread faster than conciliatory messages and get you more dopamine posting those.
Just my $0.02.