There really is no inappropriate time to celebrate the life and valor of Maryland abolitionist Harriet Tubman, and since the official establishment of Black History Month by President Gerald Ford in 1976, February has become a particularly fitting period to commemorate the woman who earned the nickname of Moses for her successful liberation of more than 70 slaves by way of the network of secret routes and safehouses known as the Underground Railroad.

But while there’s no inappropriate time, there are certainly inappropriate ways, and one Boston-based bank has struck upon a remarkably tactless one. The African-American-owned OneUnited Bank, founded in 1968 as the Unity Bank & Trust Co., elected to observe the month by issuing limited edition Visa Debit Cards featuring Tubman’s likeness as what the company calls “a symbol of Black empowerment.” And while that alone may not have caused an uproar, the image portrays Tubman as displaying the Wakanda...