Three cheers for Police Commissioner James O’Neill for standing tall where New York’s political leaders have waffled by announcing he won’t march in next month’s Puerto Rican Day Parade.

The reason: Guest of honor Oscar López Rivera, hailed by organizers as a “national freedom hero,” is a “terrorist,” the commisioner says. Added O’Neill: “I cannot support a man who is a co-founder of an organization that engaged in over 120 bombings.”

Particularly when so many of those attacks by OLR’s pro-independence FALN claimed police officers as victims.

That hasn’t stopped Mayor de Blasio, who plans on marching, or Gov. Cuomo, who says he’s “inclined” to march but is still thinking it over.

What’s to think? JetBlue and the Yankees on Monday became the second and third corporate sponsors to pull out, following Goya Foods, which had supported the parade since it began in 1958.

The Lieutenants Benevolent Association is urging a boycott of any firm that supports the event, which now include AT&T, Coca-Cola and the Daily News.

And the list of law-enforcement groups refusing to participate is growing longer by the day. It now includes the NYPD Hispanic Society, the Gay Officers Action League and the Rafael Ramos Foundation, named for a slain police officer.

The reason why is clear to them, if not to de Blasio, Cuomo or OLR’s loudest champion, City Council Speaker Melissa Mark-Viverito.

Ironically enough, MMV on Monday morning led a rally to support the honoring of OLR.

The FALN waged violent war against America, especially New York, in the ’70s and ’80s, including the bombings of Fraunces Tavern, which killed four, and 1 Police Plaza, which permanently maimed a cop.

Organizers claim honoring López Rivera will “create awareness on issues.” Nonsense: As Puerto Rican salsa legend Willie Colon wrote on his blog, “waging war against innocent civilians is a crime against humanity.”

Honoring López Rivera, who was freed from prison when President Barack Obama commuted his sentence, sends precisely the opposite message.

That’s the sole issue. Why don’t Andrew Cuomo and Bill de Blasio get it?