Many of those comments have since been deleted and at least one user deleted an entire Twitter account.
But the tweets live on, some still posted online while others have been preserved in screen captures.
Here are some of those tweets and the reactions to them:
At least some of those who reacted to the tweets issued mea culpas afterward.
“I took NPR out of context and had a stupid moment,” wrote D.G. Davies, who had accused the network of condoning violence. “Never underestimate one’s capacity to learn. Sometimes it’s painful. But it’s valuable above pride.”