Editor's note: Etan Thomas is a poet and author who plays basketball for the NBA's Atlanta Hawks. He is a peace activist and actively supported Barack Obama's 2008 presidential campaign. His website is http://etanthomas.com/

(CNN) -- Donald Trump's most recent challenge to President Barack Obama took me back to my collegiate years at Syracuse University. I had studied for two weeks straight for a calculus class, harder than I had ever studied in my life. After I completed my exam, I was confident that all my hard work had paid off.

But the next day, my professor greeted me with accusations of cheating, saying three-fourths of the class had flunked. How could I possibly have managed to get a B minus without cheating? Thankfully, not all of my professors were cut from this same cloth, but I had my share of run-ins. One professor asked me on the first day what I was doing in his classroom, and shouldn't I be in remedial English or Rocks for Jocks?

Why did I have to prove myself worthy of being in their classrooms? The vast majority of professors at Syracuse University were not like this, but the sting of disrespect from those encounters has resonated with me till this day.

Donald Trump questioning the president's educational background took me back to those unfortunate memories.

President Obama graduated from Columbia University in 1983 with a degree in political science. He went on to Harvard Law School, where he graduated magna cum laude and was the first black president of the Harvard Law Review. But apparently Trump is not impressed. He suggested -- without offering any proof of this baseless claim -- in an interview with The Associated Press that not only was he a poor student, he didn't deserve to be admitted to the Ivy League universities he attended.

Michael Eric Dyson described this situation perfectly when he said on "Face the Nation": "Skepticism about black intelligence and suspicion about black humanity have gone hand-in-hand throughout the history of this country in feeding the perception that black people don't quite measure up."

I don't think any other president in the history of the United States ever had his citizenship cross-examined, his religious faith challenged or his educational achievements put to question.

Trump rejects allegations of racism

Is Trump fanning the flames of ignorance simply for personal gain, or does he truly believe President Obama has to continually prove himself worthy?

Unfortunately, Trump isn't alone. In a CNN.com article headlined "Potential GOP presidential candidates react to bin Laden's death," Mike Huckabee, Mitt Romney, Tim Pawlenty, Michele Bachmann, Sarah Palin and Rick Santorum all gave statements about bin Laden's death. Only Tim Pawlenty mentioned President Obama by name, and he had to include that it was, in fact, "President Bush who promised that America would bring Osama bin Laden to justice."

Now, did some of the terrorists captured while Bush was in office reveal pertinent information that helped identify Osama's courier? Did this information lead the Obama administration to the compound where bin Laden was hiding? Maybe.

But isn't it also true that it was the wisdom and insight of the president that led to the abandoning of the Bush approach of bombing the entire area, leaving no man, woman or child standing? Didn't the decision by President Obama to use special forces and a surgical helicopter attack help prevent the loss of many civilian lives?

By removing Osama bin Laden, President Obama has accomplished what Bush couldn't do in two terms, no matter what he promised. So why is it still so difficult for the right to give him respect and credit?

The president should not have to prove anything to anyone. Yet, he has handled every unmerited insult with nothing but grace and class. He has risen above every act of insolence, and proved them all wrong. There is, as CBS' "Face the Nation" host Bob Schieffer described, "an ugly strain of racism that's running through this whole thing."

Going back to "The Donald": I don't think he is some cross-burning, Confederate-flag-waving racist. But I do believe he is a "Hey, what is that black guy doing here?" racist. He is the type of racist who wants black people "to stay in their place."

It is a sad situation that a man who has earned a degree from Columbia University, graduated magna cum laude from Harvard Law School, has been elected as president of the United States and received a Nobel Peace Prize has to continuously prove himself as a man worthy of respect. He simply shouldn't have to.

The opinions in this commentary are solely those of Etan Thomas.