"I have to tell you," a woman said, "[the card issuer used by the CU] is the worst offender." She went on to describe an unfair practice she had experienced at the hands of the issuer.

The credit union reacted with a move from the social media playbook: address criticism! However, it dropped the ball by offering the commenter boilerplate about working with the CU to restructure her loans.

No thank you, she replied, adding that she had just wanted the CU to know that the credit card it offers "is terrible."

The credit union took 10 days to respond. "Good news!" it said. As of Feb. 22, the unfair practice the commenter had complained about would cease.

Her retort came five minutes later: she had already closed the account. Furthermore, she said, she was disappointed to see that members no longer had access to a network of free ATMs.

Is that true? If so, it's time for me to close my accounts with the credit union, said another member commenting after her.

Well, is it true? Shockingly, the credit union never responded. Perhaps it decided to cut its losses from the tussle with the unhappy former cardholder and move on. And so the fumbled exchange of comments, preserved in the backlogs of the Facebook page for others to come across, ends on a note of member confusion and credit union silence.

It's been said a hundred times before: It only takes one negative comment to damage a brand's image.

I'm living proof of that.

I don't swallow customer complaints whole, but I do check them out. My credit union has a bad credit card program? That concerns me, since I had planned on applying for a card billed as perfect for helping young adults build credit. It was in my own best interest to research the allegations.

I conducted a litmus test. Was my credit union listed on CreditCardConnection.org? Its five criteria for an ethical card program are straightforward and commonsensical. My credit union failed. It was not among those recommended by the site. But another CU I am eligible to join was. I had originally ruled it out of my search for a credit union to call home because its branch locations are farther away from my apartment. But now it was back in the picture in a big way.

It only takes one negative comment to lose a potential credit card account. I have that outspoken former member to thank for steering me away from a product that would have likely caused me headaches.

Could my credit union have handled the confrontation better? Absolutely. It should have responded more directly and candidly instead of blithely sticking a Band-Aid in the form of a toll-free number on the boo-boo. And it certainly should have set the record straight on free ATMs. But could it have said anything to change her mind about its credit card program? Maybe not. How do you defend something that might just be indefensible?

At least one thing seems clear: Don't throw stones at banks if your own product offerings are made of glass.