I think the ad is too vague about the reason " millions of dollars have been lost" and why people have to declare bankruptcy.
and "They are lying." is too strong to say about your erlliche brother inlaw. Add a sentence that
"Even if the user of the card is an erliche yid, with a seemingly good business, something may happen that makes him unable to pay the card even for one month and that will cost YOU interest. And if they stop being able to pay your card at all, YOU are responsible to pay off the cc with YOUR money. "
Perhaps also add that they will not legally be able to dispute the charges.