Gossip, Slander, And Following The Crowd

Gossip: Monkey see, monkey do.

Remember that most people (including ourselves) tend to follow the "lead" of other people around them. For example the way people are moving in a crowd. If we look at the way people dress from era to era, and listen to the way they talk from generation to generation and region to region, it becomes pretty clear just how much we follow other people's leads. Even subtle body movements in a small group will be mimicked by others; it's nothing to be ashamed of, it's just how we are. "Monkey see, Monkey do".

Whatever is 'acceptable', apparently, for foolish, irresponsible, destructive, or rude behavior in any given group is because someone is "leading" and others are following; it's "okay" to drink one glass of wine with lunch, but if you drink two, you're doing something bad... while in another group, they're all having two glasses, but NOT THREE...no no, never three... And in yet another group, they're all smoking marijuana, but they don't smoke cigarettes.. and in another, they smoke cigarettes and drink, but they don't smoke marijuana... etc., you get the idea.

Whatever is "acceptable" Social behavior also goes the same way of following. Mark tells jokes that are demeaning to Polish people, and we all follow his lead. But when Sal tells a joke that's demeaning to French people, we all get offended.
Mark is recognized in the group as a "leader", a "cool kid", and Sal is not. The key words are "WE ALL". When Sarah tells mean blond-haired-ancestry jokes, we are all expected to accept it, including the blond people. But when Henry tells jokes about African-ancestry-people, everyone gets offended. Again, Sarah is a "leader" in the group, and Henry is not "cool enough". But there is a day that Sarah tells a joke that demeans Native Americans, and everyone is expected to laugh, and most of them do.

SO IT GOES with Gossip and "Smear Campaigns". People go along with them because the group they're in already accepts gossip and slander, because they are following someone's lead. Those who are accepted as "Leaders" or "cool kids" can slander and gossip till the cows come home, and people in the group will just go along with it, not questioning, not stopping it, usually exacerbating it like the game "Telephone".
But if one of the people in the group who are not one of the "Cool Kids" started gossiping or smearing someone, they'd probably ignore him, or defend the person he's talking about.
They'll also ignore him or argue with him if he's talking about something "bad" that someone REALLY DID.

People tend to mimic the way others TREAT OTHER PEOPLE as well. So if Jane starts talking over Cheryl, others will talk over Cheryl as well. If Jerry tends to treat Luke with disrespect, others in the group will often follow his lead. If Sharon and John treat Jeffery like he's some kind of "Leader" who deserves extra respect for some reason, others in the group are likely to follow their lead.

Humans mimic and follow others, especially those whom they consider having equal or higher "status" than themselves.
They tend to purposely ignore and counter those who they are trying to make into "lower status" members of the group.

Obviously, some do this behavior more (much more) than others, and some do it much less than others.