"It's tragic that Starbucks is going to lose customers ... for training that should be done every day of the week, every hour of the day," Rensi said on "Squawk Alley."
Starbucks should never have gotten itself "in a position like this" in the first place, he adds.
The coffee giant will close more than 8,000 of its U.S. locations for several hours on Tuesday afternoon to conduct anti-bias training. The course — offered to its more than 175,000 employees — is aimed at addressing the issues surrounding the arrests last month at a Philadelphia Starbucks of two black men waiting for a business meeting.
"Treat people the way you want to be treated," said Rensi, also formerly CEO of barbecue chain Famous Dave's of America. "To have police come and roust out two black men in your facilities is unconscionable."
However, he said he would never have closed the stores for the training "because that means I'm making a lot of customers angry."
Earlier on CNBC, Andy Puzder — formerly chief executive of CKE Restaurants, the owner of the Hardee's and Carl's Jr. chains — questioned some of the steps Starbucks took as part of its anti-racial bias campaign.
Puzder, now a policy advisor at the pro-Trump group America First Policies, argued Starbucks' new policy allowing anyone, even if they don't buy anything, to sit in its cafes and use the restrooms may have been a mistake.