Dr. Ben Carson Ripped for $2 Harriet Tubman Crack ... HE Needs Brain Surgery

Dr. Ben Carson took a huge shot at Harriet Tubman when asked about her bumping Andrew Jackson off the $20 bill -- and now he's getting blasted by another historic woman's family.

If you missed it ... the ex-prez hopeful went on FOX Business channel and not only sang the praises of our 7th president, but suggested Tubman be relegated to the $2 bill.

Rosa Parks was also in the running to get a new spot on U.S. currency, and her niece, Sheila Keys, tells TMZ ... Carson "needs surgery on his brain" and clearly puts zero historical value on Tubman's contributions to America.