This is depressing:

Cops busted a lone protester — angry with subway ads equating enemies of Israel as “savages” — as she spray-painted over one of the controversial signs today.

A Post camera crew captured the bizarre conflict between suspect Mona Eltahawy, 45, and a woman defending the ads.

“Mona, do you think you have the right to do this?” said Pamela Hall, holding a mounted camera as she tried to block the barrage of spray paint.

“I do actually,” Eltahawy calmly responded. “I think this is freedom of expression, just as this is freedom of expression.”

Hall then thrusts herself between Eltahawy’s spray paint and the poster.

Eltahawy — an activist who has appeared on MSNBC and CNN — engaged her in an odd cat-and-mouse dance, spraying pink every time she had an opening.

“What right do you have to violate free speech,” Hall pleaded.

“I’m not violating it. I’m making an expression on free speech,” an increasingly agitated Eltahawy shot back.

I take that back: it’s not depressing, it’s infuriating. Eltahawy is an American Muslim journalist. She has every right to denounce the provocative subway ads. But she has no right to deface them, and to thereby deny the right of the ad buyers to express their legally protected opinion. This is the equivalent of answering speech you don’t like by screaming so loud nobody can hear your opponent, then claiming that you were simply exercising your own right to free speech.

The fact that a journalist, of all people, doesn’t understand this basic lesson of First Amendment etiquette is appalling. Does she actually think she’s doing the Muslim cause a favor by this? All over the world, Muslims are calling for the imposition of blasphemy laws in the West. People have the impression that Muslims cannot tolerate speech with which they disagree. Mona Eltahawy, a Westernized American Muslim, gives aid and comfort to people who believe Islam itself is the problem.