Where did Maher get the idea he could say that word?

Here’s a good rule of thumb for aspiring comics. Whenever you are compelled to say, “Hey, it was a joke,” it probably wasn’t. At the very least, it didn’t land like one.

Bill Maher is an accomplished comic, not an aspiring one, but he deftly illustrated that rule Friday night on his HBO show, “Real Time with Bill Maher.” As you’ve surely heard, Maher was interviewing Republican Sen. Ben Sasse, who invited him to come to Nebraska and “work in the fields with us.” Maher’s riposte? “Work in the fields? Senator, I’m a house n——r.”

Some people — including Sasse — laughed. Some groaned. “It’s a joke,” said Maher with a dismissive wave of his hand. A day later, he issued a statement proclaiming himself “very sorry.”

Which is well and good, but doesn’t answer the most vital question: where did he get the idea that word was okay for him to say? Yes, he has a constitutionally protected right to do so; that’s not at issue. One simply wonders where he got the notion he could get away with it. Maybe it’s the same place he got the notion he could get away with calling Sarah Palin a “c—t” back in 2011?

Maher, of course, is just the latest high-profile comedic fail. Kathy Griffin is still smarting from the beating she took for a jarringly offensive picture of her holding up a prop meant to look like the bloody, severed head of Donald Trump. But ugly as that “joke” was, it is of a different kind than Maher’s transgression.

What he did is more of a piece with Stephen Colbert’s homophobic quip about Trump’s mouth and Vladimir Putin’s man parts. Or his old “Ching Chong Ding Dong” routine, which offended many Asian Americans. It calls to mind Seth McFarlane’s sexist “We Saw Your Boobs” song at the 2013 Oscars, which appalled many women. And Daniel Tosh’s 2012 “joke” about an audience member being raped.

We are not here to argue whether those men are or are not racist, sexist or homophobic. That’s immaterial. No, we are here to deconstruct the sense of privileged, white, male, liberal entitlement that allows them to feel they can say and do such things in the first place.

Yes, humor is rude, comedy is shock and funny is whatever works on a given night. Yes, satire is the art of undermining an asinine belief or behavior by magnifying or pretending to agree with it. Yes, the business of laughter is the business of crossing that completely subjective, always moving line of decorum and propriety.

And yes, occasional failure is inevitable. Ask Kathy Griffin.

But with all that duly conceded, imagine for a moment it was Rush Limbaugh who made Bill Maher’s joke or Sean Hannity who sang Seth MacFarlane’s song. The right wing is known for its hostility toward African Americans and women, so the outrage would have been visceral, immediate and loud. Many of us would have rightly decried “jokes” that bully and demean marginalized peoples.

Yet that fury feels muted or altogether absent when such jokes are told by the left-leaning likes of MacFarlane and Maher. Lacking the right wing’s baggage of racial and gender hostility, they escape — or expect to escape — relatively unscathed.

But why? Because they’re on “our” side? Because they’re just joking?

Those of us who are marginalized and those who simply care may want to rethink that blank check forbearance, given that a smarmy white comic now feels free to declare himself “a house n——r.” If your ancestry traces to slavery, you might well ask: is this guy laughing with us — or at us? And that’s the problem.

These days, it’s hard to tell.