"Yes, absolutely. I'd take the wall down," he told MSNBC's Chris Hayes in an interview from a spot overlooking the border and Ciudad Juárez, Mexico.
Hailing that bollard fence during a campaign rally Monday night in El Paso, President Donald Trump called it proof that "walls work." But O'Rourke, pointing to violent crime rates, said the fence's construction in 2008 "didn't make us any safer."
The former congressman from Texas, who is weighing a bid for the 2020 Democratic presidential nomination, criticized Trump's anticipated decision to declare a national emergency in order to fund his border wall.
"It's hard to make a rational case for an emergency declaration or troops on the border or any amount of additional border walls or border fencing or steel slats," O'Rourke said.
He also called actions to beef up border security since 9/11 -- including construction of the border fence -- "perverse."
"We do this, whether it is the war on terror, the war on drugs -- we project our fears and anxieties to places like El Paso, to the US-Mexico border, and punish the people who live here. There's no reason to do that. But it is the fear and the anxiety that is stoked by people who should and frankly do know better that results in these policies," he said.
He said the United States can be made safer by "treating people with dignity and respect -- not militarizing communities, not adding even more to the $20 billion a year that we're spending on border security."