they can sell at a Knicks game

[Ostap]

White supremacists are like babies on a plane. Even one is enough to ruin your day. And you do notice, you do notice, that Tucker Carlson only gives white terrorists this pass, yeah? Like after 9/11, he wasn't like, "Al Qaeda, please. What was it, like 19 people? Is this a real thing, huh? It was like 19 people. Call me when they can sell at a Knicks game, okay, uh-huh."
link with timecode The Daily Show with Trevor Noah

Hello to all. What does the whole boldfaced part mean? The Knicks are a popular basketball team, but apart from from that, it's unclear.

 

[probus]

It's not "sell at a Knicks game". He says "Call me when they can sell out a Knicks game". Madison Square Garden, where the Knicks play, can hold a great many people.

By the way, this kind of humour would be utterly wasted on Carlson. He's quite oblivious to it.

 

[Tarheel]

It's not "sell at a Knicks game". He says "Call me when they can sell out a Knicks game". Madison Square Garden, where the Knicks play, can hold a great many people.

By the way, this kind of humour would be utterly wasted on Carlson. He's quite oblivious to it.

You mean that's humor? (It's wasted on me too.)

 

[Ostap]

He says "Call me when they can sell out a Knicks game". Madison Square Garden, where the Knicks play, can hold a great many people.

With "sell out" the sentence now indeed makes more grammatical sense, but could you please explain the point of the joke? I still don't get it.
And who are "they"?

 

[probus]

In my opinion the joke is in very poor taste and not funny (as Tarheel pointed out). Of course the events of September 11 were tragic and horrifying. Minimizing the importance of 19 deaths by comparison with the capacity of Madison Square Garden doesn't strike me as humorous.

 

[SoothingDave]

It's not 19 deaths. The unfunny Noah is trying to make a comparison about the small number of people who actually committed the 9/11 terror attacks and Carlson's noting the very small number of actual "white supremacists" in the US. The US left needs a boogieman, and their focus is always on the very fringe remnant of actual racists in the country.