“I think what’s most reprehensible is his implication that Kenneth Bae, an American detainee on very spurious charges, who deserves to come home, might be guilty,” Richardson, a former governor of New Mexico, said on CNN’s “New Day.”
Rodman has made headlines by visiting North Korea, where he has been seen with that country's leader, Kim Jong Un.
During a Tuesday interview on CNN, he suggested Bae deserved imprisonment when he was questioned about whether he would seek Bae's release.
The outburst has drawn criticism across the political spectrum. Richardson tried to rescue Bae last year during a trip to North Korea with Google Chairman Eric Schmidt.
Rodman has been in North Korea this week with a group of retired basketball players on what he has described as a basketball diplomacy tour.