Was it that they posted a picture of the staff of Imgur that hatemail was sent, or was hatemail sent because Imgur just decided to wipe them out?
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Did FPH cross the line with the pic. Mostly yes... But they didn't put personal information on it. Nor was it an drive to attack them. (It was done in satire [even "the dog is fat"]
Imgur is a private website that can moderate content as it sees fit. They didn't want to be associated with a hateful community, imgur generally tries to encourage positivity from what I've seen.
The appropriate response is not to harass people. It's amazing how difficult that concept is. What might seem like "satire" to you is pretty messed up behavior, and in others contexts would be an outright threat
Seems like strong endorsement to me