Wilder, 33, said he was "trying to get a body on my record" before defending his WBC title against compatriot Dominic Breazeale on Saturday.
"This is the only sport where you can kill a man and get paid for it at the same time," said Wilder. "It's legal."
Wilder has made similar comments in the past. In March 2018, British heavyweight Tony Bellew called him a "disgrace and senseless idiot".
Earlier this year, after Wilder told Breazeale to "make some funeral arrangements", promoter Eddie Hearn said: "It's bad for the sport."