The gossiper supply information to whom they are attracted, and with whom they wish to align themselves. Negative gossip about third parties, who of course have no opportunity to defend themselves, is a dangerous game that can rebound on the gossiper. To be good at malicious gossip requires a high degree of subtlety and skill. The trick is to appear to be sympathetic to the victim while holding him below the water-line with implicit denigration. Most people find this distasteful.
Much malicious gossip is conducted unconsciously, an act that requires self-deception.
In the world of gossip, self-deception often takes the form of genuinely believing one is on the high moral ground of charitable sympathy, looking down on one's slowly sinking victim. Nature abhors a vacuum and the gossip rushes to fill it.