LONDON — The Oxford Union, a prestigious, nearly 200-year-old British debating society that counts several high-profile politicians among its alumni, has come under fire for the violent treatment of a blind student from Ghana who witnesses say was forcibly expelled from a packed event hall .

The incident has ignited outrage around the country, provoking a wave of resignations from the society and drawing scrutiny of the elite, predominately white organization, especially as videos have spread online showing the student, Ebenezer Azamati, struggling with a security guard who forcefully tried to pry him off a bench .

The society’s president, Brendan McGrath, stepped down under growing pressure late Tuesday, saying that he apologized “profusely and unqualifiedly.” In his resignation letter, he added, “Fundamentally, it is the president’s job to ensure that every member feels welcome at the Oxford Union. This is a goal I have manifestly failed to reach.”

Image Ebenezer Azamati, 25, a postgraduate student at Oxford University. Credit...

At least eight other society members resigned this week, including several in leadership roles.

Mr. Azamati, a 25-year-old postgraduate student at Oxford University who is a member of the union, said in a phone interview that he was traumatized by the event, which took place on Oct. 17, and that he wa s considering legal action .