Should I speak up when I see something offensive or false on social media?

With all the ranting and raving, it's easy to feel that sensible online debate is impossible. But people are watching, and sensible voices need to be heard

Q: When someone posts something offensive or factually wrong on my social media feed, how obliged am I to wade in and correct them?

A: There are words and aphorisms to describe doing nothing in the circumstance to which you refer. "Bystander syndrome" is one, the phenomenon of witnessing an attack, verbal or physical, and standing passively by. When I was at college, spotty men wielding clipboards would loiter outside the dining room on the day of student elections, informing their uninterested peers that "apathy led to the rise of Hitler". These days, we are more likely to reach for a line sometimes attributed to the philosopher Edmund Burke: "All that is necessary for the triumph of evil is that good men do nothing."