Insecurity And Safety In Numbers

Insecure, immature people NEED "safety in numbers", so they will often turn against a person who does not completely go along with all of the dynamics of the group they're in. Especially a person of the same sex.
Expectations are usually very high toward those of the same sex (same sex as a controller person) to go along with 'the group', and to obey the leadership and hierarchy of the group, no matter how small or informal.

A person who refuses to conform to the group will first be talked about behind their back in a negative way, with one member pleading a case about how "bad" (selfish/stuck-up/uncaring/crazy, etc.) the other member is, trying to get others to agree with them.
(They will say that they were 'venting', or 'just talking', but 'venting' does not result in a person being targeted for ostracism by the group. If the original person WAS actually seeking support, then it's another member of the group who twists it into an opportunity to launch a "dislike campaign" against the person being talked about. A healthy group would be supportive of both the "venter" and the person they were "venting" about).

~The motive is rarely about something serious the person has done, this kind of behavior is nearly always about a person deflecting blame off of themselves and trying to put it onto the person who they did something to, even if the thing was trivial. The 'trigger' is usually a feeling of embarrassment, shame, or resentment on the part of the person who is launching the 'attack'.

Then, when enough members of the group have been recruited, the targeted person will be "ganged up on" with social signals and social "punishments" in order to make them FEAR rejection, and re-think their refusal to conform.
If that doesn't work, the person will then be talked about MORE, and others will be recruited to join the campaign against them.
When members of the group feel secure enough, because they are being "backed up" by other members, they will then carry out the "Rejection" and "Ostracism" process.

Women do tend to do this more than men because of the very different ways they are socially conditioned and raised during childhood. HOWEVER! Women tend to socially manipulate and attack other women for not conforming to their group, or for refusing to be controlled or bullied by an individual woman;  but men ALSO socially manipulate and attack individual women, just because they've learned that it WORKS. It doesn't work NEARLY as well against MEN, because of the biased culture.

Both immature men and women are more likely to go along with smearing a woman than a man, and both men and women are more likely to defend a man against gossip.
That's because they have learned about the different CONSEQUENCES that they WILL or WILL NOT receive for "speaking against" or smearing women vs. smearing men.
Men tend more to directly bully and reject other men they've targeted, without creating a large smear campaign; not because they're "more moral", but because there are often consequences from others for smearing a man.
So both men and women who "smear" will do it to a woman much more often than they'll do it to a man, because they know they'll get away with it.

Which brings the subject back to immaturity, insecurity, and Narcissism. Those who ONLY STOP THEMSELVES from doing certain destructive, immoral behaviors (such as ostracism, slander, and bullying) because they FEAR THE CONSEQUENCES that might result are often seen doing many other kinds of destructive, manipulative, illegal or deceptive things. They gauge how far they can go, and what they can "get away with" when they're making decisions.

Going Along With The Crowd

Those with Narcissism, and also those who simply lack maturity, tend to judge people and things by how other people act, and what other people say.
So if they liked a new person at first, but later it looks like they person is not popular, they will usually reject the person.

It's about being accepted, liked, admired, or feared; most N's want to be associated with "popular" or powerful people, and so will reject and avoid "less popular" individuals in order to avoid being associated with them by the crowd.

One of the main reasons Narcissists will make up cruel rumors about a Target is to avoid being seen as a "popularity whore". They have to make up an excuse to COVER themselves for rejecting the person, so they try and spread it around that the person has 'bad character'.
(Of course, smear campaigns only work when there are other willing participants who eat the slander up like ice cream, who are too immature to stand up for the targeted person and have their back.) 


Controlling Narcissists Block Good Things

A common controller/narcissist behavior:
purposely NOT doing something, purposely NOT sharing information, purposely hiding something, purposely avoiding something that would PLEASE a Target.

For example, if a Target's favorite singer is having a concert nearby, the N. would purposely NOT tell the Target about it. They might honestly FORGET, because a component of Narcissism is being so self-centered that they tend to only remember things they want for themselves. But it shows itself to be on purpose when they are seen to remember OTHER things that might please someone they're trying to impress.

N.-Controllers will do this all the time, with all kinds of things. Anything that a Target shows interest in, or is pleased or excited by will be the very thing that gets avoided, changed, or nixed. In severe cases, destroyed.

It can be anything at all, from a Target's favorite cartoon character, to a Target's interest or hobby, to important opportunities for a Target's future or career. It can be a pair of shoes that the Target obviously likes, or a hairstyle, or a jacket.

It can be a PERSON who the Target apparently likes or has connected with, any person, including their own child, parent, partner, or a new friend or business associate.

It's one of the N/Controller's most common behaviors: BLOCKING a Target from anything (anything positive and not destructive) that pleases them, interests them, would be good for them, would be fun for them, would be a good opportunity, or would help them build their confidence.     

When children grow up around N/Controllers, either in their family or their community, they can develop the habit of blocking THEMSELVES, and avoiding, fearing, or resenting and rejecting positive things. (Some who end up developing N/Control do this to others instead of themselves, repeating the pattern).

Selective Compassion

Humans tend to sympathize selectively, not universally. Bias is usually about one's own identity, so people tend to have "compassion" and "understanding" for those who are more like themselves and those they like, but only have negative judgment and self-righteousness toward those who they view as "other", not like themselves, and those they feel resentment or envy toward.

This selective compassion is common for humans, but many are capable of maturing past this developmental block. Those who have Narcissism can not, because they are unable to admit that they have any "flaws", and they believe that their biases and prejudices are "correct".