Cardi B Photo: Facebook

The concept of the civil rights-themed comedy sketch was simple. Whether it was funny or just plain offensive remains in the eye of a growing number of outraged beholders.

In the sketch - an unaired clip was shared by TMZ and posted on YouTube - the "Real Housewives of the Civil Rights movement" get together to plan a rally for Martin Luther King Jr., because, as one says, "nothing can go wrong for Martin in Memphis."

But in reality, the skit from the show "Off the Rip," which doesn't have a network or a premiere date, was actually jokes about King's infidelities. Rapper Cardi B played King's widow, Coretta Scott King, and delivered the key punchline:

"All these hussies want to sleep with my husband," she said in the sketch. "But it's OK, because I know he marches home to me."

King's children were not amused - especially because the video spread on the 55th anniversary of the March on Washington and the civil rights leader's "I Have a Dream" speech.

The speech called for economic and civil equality, and an end to racism, critics said, but the rapper was using King's legacy for cheap laughs.

"They paid an extraordinary price so people of colour can have a platform- & this is how you use it," King's daughter, Bernice, the chief executive of the King Center, tweeted on Tuesday. "(Cardi B): Let's talk."

And the civil rights leader's son, Martin Luther King III, who commemorated his father's speech with words of his own at the U.S.-Mexico border, lashed out at Cardi B and at TMZ.

"Today I'm at the border, addressing families and children that are being separated - important issues. And yet TMZ and others choose to deal with the superficial," he said. " ... First of all that's not my mom. My mom didn't talk like that. So it's all fictitious, kind of garbage, and the unfortunate part is that young people look up to these artists, and believe that whatever you put on television is truth."

History has deeply analysed King's infidelities, as new information helps shed light on the imperfect people at the heart of the nation's defining moments (see: Thomas Jefferson). Others have examined FBI Director J. Edgar Hoover's attempts to discredit King, and the infamous letter that sought to shame King into committing suicide.

But is there a line even comedy shouldn't cross? When is an attempt at satire simply disrespectful?

It was unclear why the original "Real Housewives of the Civil Rights movement" video was leaked by TMZ. But the people involved in it spent the hours after TMZ released the clip on an internet-based apology tour.

Although Cardi B didn't publicly say anything about the flap, she apparently apologized to Bernice King, who tweeted her thanks:

"Thank you, @iamcardib, for reaching out to me and apologizing for the skit that aired on @TMZ. I look forward to talking with you soon."