Arum's anger comes from Hearn vying to promote a fight involving Lopez, who is part of the Top Rank umbrella headed up by the American promoter.
Arum recently stated that the Lopez-Kambosos Jr. bout was "not a marquee fight" which led to Top Rank allowing it to go to a purse bid.
Matchroom-Hearn placed a bid of $3,506,000, while Top Rank-Arum offered $2,315,000. In the end, both were blown out of the water by the social networking App, Triller. They came in with an offer of $6,018,000, which comfortably saw them earn the rights to present the fight.
After Arum claimed that it was "bad policy" for Hearn to take part in the purse bid, the Matchroom supremo told BoxingScene.com that Top Rank "let it get to this":
"Teofimo Lopez took the chance for small money to fight Lomachenko because he believed he would win and he believed he would get the financial rewards he deserved. But guess what? When he won, they wouldn't give it to him. And this whole problem has been caused by Top Rank.
"You know, Bob's been out there, 'Oh, Eddie Hearn, I'm f--king pissed off that he's bid and he's gotta watch himself now.' F--k off! It's an open market. If you can't do a deal with your fighter, and that comes into the open market, you pay the consequences. And the consequences is someone else has popped up from nowhere and taken one of your biggest assets on your platform, for ESPN, and put it on another platform. It's a disaster for Top Rank.
"I told him I'd bid. You know why? Because they tried to put the fear into people not to bid, and that's not [acceptable]. Once you do that, all bets are off. If you would've come to me, sat down - but what you're doing is you're taking opportunities away from your client. So, you want no one to bid so you can get your guy cheap? Is that what you want?
"It doesn't work like that. We had an opportunity to bring one of the biggest names in the sport to our platform in the open market. Don't tell us what we can and can't do. But it's irrelevant anyway.
"Let's start respecting the fighters. I hear too much talk at the moment of, 'The fighters have gotta get less money. We've gotta bring the purses down.' And I understand we've all got businesses to run. But understand one thing - we're not putting our lives on the line in the ring. We've got a nice life. Bob Arum's got money. [Top Rank president] Todd duBoef's got money. Matchroom has got money. I've got money.
"Let's not be arrogant enough to start thinking that we can, you know, gamble with the livelihoods of fighters. And I see too many [negative] comments from Bob about Crawford, about Lopez. I mean, these guys are pound-for-pound superstars."
Top Rank in trouble?
This outburst from Arum comes not long after he criticised Terence Crawford following his victory over Kell Brook in November 2020.
It is an odd tactic for him to play down the credentials of some of his top fighters. Lopez is on track to become one of the biggest stars in boxing after his career-making win over Vasiliy Lomachenko.
It is quite foolish on Arum's part to let his latest fight go to purse bids. The fact that he has targeted Hearn may just be sour grapes, but it is hard to argue that it was not just fair game for the Brit to place an offer.
This is a big win for Triller and boxing as a whole. It shows that even at this difficult time, there is still a keen interest in the sport from broadcasters and fans.
You worry for Arum-Top Rank though, as he is stepping down a dangerous road with how he is criticising his own fighters.
Crawford and Lopez are great boxers and if used properly, they will be real assets to Top Rank in the years to come.
But if they are not treated correctly and let slip, promoters around the world will be desperate to secure their services.
To make it worse, Hearn will be right at the front of the queue, which will peeve Arum even more!