Cousins and others Rockets players did not directly address Harden in news conferences earlier this season after the eight-time All-Star requested a trade from the team, showed up late to training camp and failed to build chemistry with new teammates.
But Cousins opened up about the experience when he met with reporters on Wednesday after the news broke that Harden had been sent to the Nets as part of a three-team trade that also involved the Cleveland Cavaliers.
Cousins responded to a question about whether he felt slighted by Harden's comments on Tuesday that the Rockets were "just not good enough" to compete with the Los Angeles Lakers.
"Obviously, it's disrespectful, but everybody has a right to their opinion," Cousins said Wednesday. "We feel a certain type of way about some of his actions.
"This is the nasty part of the business that kind of gets swept under the rug. You deal with some of these things. When guys are in positions of being franchise players or whatever the case may be, it's usually sometimes a nasty breakup."
Cousins also said Harden's "approach to training camp" and "antics off the court" were disrespectful.
"This isn't something that all of the sudden happened last night, but with that being said, this is the nasty part of the business," Cousins said. "It is what it is."
Harden held out at the start of training camp. He was seen partying maskless in Las Vegas and Atlanta while his team prepared for the season. He was later fined $50,000 by the NBA for violations of the league's health and safety protocol for COVID-19.
Harden averaged 17.4 points per game in his final five appearances for the Rockets, his lowest scoring output for a five-game stretch since he joined the team in 2012. The Rockets lost four of those five games and are 3-6 this season.
The Rockets landed former Cavaliers guard Dante Exum, former Nets forward Rodions Kurucs, four first-round picks, and four first-round pick swaps in the Harden deal.