Jake Paul was enraged over the outcome of KSI's most recent fight, which ended with a controversial second round knockout of Joe Fournier.
At the OVO Arena Wembley in London, KSI collided in the ring with the 40-year-old Fournier, who has an unbeaten 9-0 record as a pro, with all of the wins ending by knockout.
During the second round, it initially appeared that KSI knocked Fournier out with a two-punch combination - but several replays clearly showed an elbow connecting with Fournier's jaw, which sent him down and out.
Paul, who is KSI's rival, believes the fight should have been changed to a no-contest or disqualification.
"I respect boxing too much to respect what that was. If that was indeed a real boxing match it will be ruled a no contest or disqualification," Paul stated on social media.
Fournier agrees, and wants the fight to be overturned.
He raised a solid point, about getting a fair shake when you step in the ring with the actual promoter of the fight.
“He cheated, it's clear, you've all seen the replays. He hit me with a clean elbow. When you're fighting the promoter on his own show - I've never been cheated like that," Fournier told Fred Talks Fighting.
After the fight, KSI called for a showdown with unbeaten light heavyweight prospect Tommy Fury.
"I want this, I want to do what Jake Paul couldn't; knock you out," KSI said to Fury.
After trading words in the ring, Fury shoved KSI and a scuffle broke out in the ring.