Nate Diaz, in 2013, was doing something awful, and unfortunately it wouldn't be the last time. He used a homophobic slur on Twitter and it was so bad that even the UFC, which seems to tolerate a lot of bad behavior, suspended Diaz for 90 days and fined him $20,000.

"UFC lightweight Nate Diaz has received an immediate 90-day suspension and $20,000 fine for violating the UFC’s fighter code of conduct," the UFC said in a statement at the time. "The language used in his tweet was regrettable, offensive and inconsistent with the values and culture of the organization, and is not tolerated. The money will be donated to charity."

Diaz took the suspension to heart and changed his ways. He decided that being homophobic was wrong. That attacking a group of people was wrong. He said it would never happen again and was deeply sorry. He grew and learned and became a much better man.

Nah, LOL, that didn't happen because Nate Diaz would be awful again.

Read moreNate Diaz, Jake Paul hold vulgar press conference before fight

Ten years later, on the eve of his Saturday fight against Jake Paul, Diaz used an anti-gay slur again. This time it was during the pre-fight press conference on Thursday where multiple skirmishes broke out. Paul didn't exactly cover himself in glory saying if he met Diaz in a dark alley he would sexually assault him. If you were looking for high class, this was not it. This was the Bad Place.

And in a remarkably tone-deaf statement Tela Mange, spokesperson for the Texas Boxing Commission, told USA TODAY Sports by email that, "We do not regulate what the fighters say to each other or anyone else.”

Boxing isn't a place for saints. All sports and leagues have their goons. I mean, Deshaun Watson has a job. Boxing has had plenty of bad guys. I get that.

But boxing is making a bad deal with the devil by embracing Diaz. If the sport thinks Diaz is a fix for its problems, that's just dead wrong. Maybe because he's a big name he provides a sugar high, a short-term spike, but as his use of a slur (twice) shows, he's more likely to embarrass boxing than help save it.

The fact that Diaz used an anti-gay slur a second time, a decade later, shows the first time wasn't an accident (not that we didn't already know that). It's particularly disturbing because in the time since 2013 there's been a significant amount of awareness around LGBTQ issues. There's simply no excuse for not understanding the pain that's caused by using anti-gay language. Diaz knows all of this. He just doesn't care.

This likely isn't the last time Diaz does something like this. Particularly if Diaz wins his fight against Paul or it's close. The will in the sport to rein in his behavior will be low because he'll be a big draw.

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Diaz's use of a slur isn't the only recent issue with him. In April, an arrest warrant for Diaz was issued by the New Orleans Police Department on suspicion of second-degree battery, according to numerous published reports. A video that surfaced on social media apparently showed Diaz choking a YouTube personality named Rodney Petersen.

This graph from an ESPN story about the incident was pretty chilling: "Petersen, who is known for his resemblance to fellow influencer Logan Paul, could be seen in the video confronting Diaz with people fighting on all sides. Petersen appeared to engage with Diaz, who locked Petersen in a guillotine choke submission standing up until Petersen was unconscious. Diaz then let Petersen drop to the street below, where Petersen hit his head on the pavement."

Again, boxing has long had its issues and bad guys. It doesn't need another one. It especially doesn't need one who has twice insulted an entire community of people and hasn't learned any lessons.

Boxing doesn't need Nate Diaz.