WBC heavyweight champion Deontay Wilder and top contender Tyson Fury have been very critical of Anthony Joshua in the aftermath of the British star's sensational defeat.
Back on June 1, Joshua was shocked by heavy underdog Andy Ruiz at Madison Square Garden in New York City.
Joshua went down four times before the referee waved off the contest in the seventh round.
Joshua has already exercised his right to an immediate rematch, which is being lined up for the fall.
Wilder and Fury believes Joshua is finished - and they both pick Ruiz to win the second time around.
Hearn believes the opposite. He expects Joshua to get revenge and come out on top.
"Everybody has got an opinion," Hearn said Sky Sports. "Tyson Fury's comments fluctuate every day. He praised Joshua then he's slagged him off.
"Wilder's said what he's going to say, but look, it doesn't really matter. You've got to take the rough with the smooth in life. They love you when you're on the way up and they kick you when you're on the way down.
"That's just life. The ones that are supporting AJ now, they're the real people, the real fans, and he's very thankful for that support. Those same people that are encouraging him to come back are the people that are going to give him the motivation to succeed.
"The haters as well give him the motivation to succeed, but I think in Anthony Joshua, you have a great man, a great athlete, a great champion who will come back and rule again."