MSNBC host Joy Reid on Tuesday night said that only viewers of Fox News know about MS-13, and couldn't understand why President Donald Trump spoke of the dangerous gang during his State of the Union address.

What's the background?

Trump, during his Tuesday night speech, noted the attendance of two sets of parents whose daughters were killed by violent MS-13 gang members, saying that many gang members "took advantage of glaring loopholes in our laws to enter the country as unaccompanied alien minors."

He added, "I am calling on the Congress to finally close the deadly loopholes that have allowed MS-13, and other criminals, to break into our country."

Reid, in her SOTU post-mortem with MSNBC's Chris Matthews, didn't seem to understand that MS-13 is widely known — and feared — across the U.S.

"He gives a speech tonight, in which he makes it sound like the biggest issue in the United States, the biggest threat is MS-13, a gang nobody that doesn't watch Fox News has ever heard of," Reid said. "So he makes it sound like they're the biggest threat."

.@JoyAnnReid thinks nobody outside of Fox News viewers has ever heard of MS-13 before. Also, listen to Chris Matthews egg her on. What a circus. lol pic.twitter.com/ndvcACXY5v — Based Monitored 🇺🇸🇮🇪 (@BasedMonitored) February 1, 2018

What happened just a day later?

The parents of one of the slain teenagers appeared on Fox News' "The Ingraham Angle" on Wednesday night, where they spoke with the show's host, Laura Ingraham.

The slain teen's mom, Elizabeth Alvarado, expressed her astonishment over Reid's comments, saying she had "no words" over the Reid's remarks.

"These are gang members that just, you know, decided to be a judge and a jury to take my daughter out like that," Alvarado said. "It’s unacceptable. I don’t want it to happen to anyone else’s family but something needs to be done."

Alvarado also said that it was an "honor" to meet the president, who she called "very genuine" and "nice."

The victim's father, Robert Mickens, castigated Democrats who didn't stand up for his daughter during Trump's recognition of the families.

"I felt it was very disrespectful," Mickens explained. "For the simple fact that the Democrats who ... did not stand up were African Americans. So that hurts me a lot to show that they did not have respect."

"Regardless of how they feel about the president, they should show the respect because I would show them the respect if that was their loved one," Mickens added.