Either you’re with us or you’re against us.

Columbia student activists are pestering peers to attend campus protests and walk-outs in solidarity with college students at Missouri and Yale or risk social isolation, students say.

Organizers posted flyers and sent Facebook messages inviting undergraduates to wear black clothing and join two demonstrations last Thursday to support people of color who are “marginalized and threatened.”

But some students worried they would be “ostracized” if they did not participate or dress in sync, one college parent said.

“There’s been a campaign of intimidation, where students are going dorm to dorm, floor to floor and asking students to go back to their dorms and put on black if they’re not wearing black,” the parent said.

“My daughter told me people are uneasy and fearful,” she added. “Her personal politics are left-wing and she shares their sympathies, but she doesn’t like to feel that she can’t wear blue if she wants to wear blue.”

Some students felt caught between their politics and academic responsibilities.

“We support them, but we’re here to learn,” said one senior who declined to give her name. “There’s a divide among students. People who are not willing to walk out are seen as not supporting the movement.”

One freshman said, “Some students were asking if I knew about the protest and why I wasn’t there. It was just my choice. I’m not really the protest type.”

Fed up with their administration’s slow response to slurs directed at black student leaders and threats of violence, University of Missouri students demonstrated for weeks before forcing their president’s resignation on Nov. 9.

And tempers boiled at Yale, where students chastised an administrator for arguing Halloween costumes should be “a little bit offensive” and condemned a fraternity for restricting entrance to its Halloween party while chanting “white girls only.”

Hundreds of Columbia students gathered at the South Lawn Thursday, and some speakers heckled bystanders who did not participate.

“Look at those guys playing Frisbee — that is the definition of privilege,” said one speaker.

The students stopped playing Frisbee and left the area.

Another student wearing a T-shirt with the words “Kill White Supremacy” called Columbia a “white supremacist institution.”

She led the crowd in a progression of chants including “I love black people,” “I love all black people” and “I love queer black people,” before adding “I love black criminals” and “I love black people who steal.”

“Raise your hand if you’re a little bit uncomfortable,” she said as a smattering of hands went up.

“It’s okay if you’re uncomfortable right now. This university was built on stolen land on the backs of my ancestors — and that is uncomfortable.”