Before participating in the violent protests at Columbia University, an affluent advertising heir named James Carlson had previously showcased his anti-Israel beliefs to a Park Slope father.

Simeon Climo reached out to Carlson — a trust fund baby and the most violent of the Columbia protest leaders, dubbed “Richie Rich” on the front page of The Post — on the neighborhood’s “Buy Nothing” Facebook page, where Carlson posted he was giving away a free baby crib.

“I put my name in to be considered, and lucky me, I was chosen to receive the crib,” Climo, who is Jewish, told The Post.

But the October exchange, which took place 10 days after Hamas’ violent attack on Israel, quickly went south.

Climo then followed up with Carlson, only to get a message that shocked him.

“Hey Simi, sorry if this seems petty but the flag on your profile pic seems to be celebrating the internment and genocide of my people, so I really don’t feel like doing you any favors,” Carlson wrote, according to a screen shot.

Climo, who had posted an Israeli flag on his profile page, shot back: “Oh you are an anti-Semite. Got it. Best of luck to you too.”

Carlson replied with another surprise.

“I’m half-Jewish, don’t speak for me,” Carlson wrote. “Wishing you compassion and understanding.”

“Hitler was part Jewish as well,” Climo retorted. “I am compassionate and I understand you are angry/hateful and looking for a place to put that hate and anger. Glad I could help.”

“You know who else is part Jewish? Rod Stewart,” Carlson bizarrely replied, according to Climo. The rock star isn’t Jewish.

Carlson’s Facebook account is now private and he didn’t answer messages there from The Post.

About six months after the exchange, Carlson was busted as one of the protesters who broke into Columbia University’s Hamilton Hall. Carlson, aka Cody Tarlow, is “a longtime anarchist,” a high-ranking police source said.

He was charged with burglary, reckless endangerment, criminal mischief, conspiracy and criminal trespassing after the Columbia arrest.

He struggled with a janitor at the school during the Hamilton Hall takeover and broke a camera inside a cell at One Police Plaza after he was detained.

Carlson was also arrested for a hate-crime assault for lighting a counter-protester’s Israeli flag on fire last month at Columbia.

The provocateur’s activities go beyond street protests.

Carlson wrote a letter to a Wisconsin federal judge in January gushing over his friend Hridindu Roychowdhury, who pleaded guilty to firebombing the office of the pro-life group Wisconsin Family Action on Mothers’ Day in 2022.

In the letter, Carlson insisted the arsonist “sees the world with nuance and sophistication,” calling Roychowdhury a “compassionate young person with tremendous potential.”

Roychowdhury was sentenced to 7-and-a-half years in prison.

Carlson’s own arrests date back to 2005. He is the son of late advertising execs Richard “Dick” Tarlow and Sandy Carlson Tarlow.

A lawyer by trade, Carlson has a baby mama who is a model and his stepmother dates rocker John Cougar Mellencamp.

The violent demonstrator has made several campaign donations in recent years totaling $1,525 to far-left Big Apple Democrats, including former Mayor Bill de Blasio, state Sens. Jabari Brisport and Julia Salazar, and Assemblyman Zohran Mamdani. 

The Transport Workers Union, which represents the Columbia custodians, plans on suing the university as well as protesters who attempted to block its members from exiting Hamilton Hall, according to the labor group’s president John Samuelsen.