Michael Phelps went on a self-described “rant,” defending his clean record in a Facebook live video Friday.

It appeared that Phelps shot back at former rival Milorad Cavic‘s anti-doping comments, eight days after Cavic said Phelps’ recovery rate was “nothing short of science fiction.”

But Phelps later clarified that he was responding to a comment that somebody made on the live chat.

“I think that comment is so rude and so beyond anything that’s really imaginable,” Phelps said in a Facebook video. “You want to go and look at any results I’ve ever had in a drug test, go ahead. … If you think I cheated, that’s your own opinion. I know what I did in the sport. I know the hard work I put in. And I know what went into my body, and drugs were not one of those things.”

Phelps, who repeated last week in front of Congress that he didn’t think he had ever competed against a clean field internationally, again voiced criticism about doping in sports Friday.

“People who test positive in sports don’t deserve another chance to perform because they’re doing something that other people are doing with training,” Phelps said. “I know I busted my tail for years on end, in training, trying to get myself stronger and ready for every race. And that’s what I did. I had goals, and I achieved them because I worked hard to accomplish them. There are other people that are taking the easy, cheap way out, and they’re taking performance-enhancing drugs. That’s a joke. Sports in this world today, in my opinion, some of them are great, but some of them are also a joke because there are so, so many people that are trying to find a way to cheat and get away with it. And it takes away from sports. It takes away from the true meaning of what sport is. And that’s sad. And for me, as a father now, watching my son grow up and watching him to get in sports or grab a ball, do this, do that, I think that’s something that I hope changes in years to come, so my son never has to go through some of the things that I went through as an athlete.”

Phelps then apologized to his thousands of Facebook Live viewers.

“Sorry I went on that rant, guys, but this is something that’s such a passion for me that has to change,” he said. “It’s so frustrating when people sit there and say you cheated, or you do it this way or you do that. You don’t know. I’m the only one that knows. And all the other thousands of drug tests and vials of blood and cups of urine that I’ve had to give, open-handed.”

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CORRECTION: An earlier version of this post incorrectly said Phelps’ comments were in response to Milorad Cavic’s comments from last week.