Donald Trump. Sara D. Davis/Getty Images Donald Trump suggested Sunday morning that he could not understand why he was earning scorn for questioning a pair of Gold Star parents who slammed him during a speech before the Democratic National Convention.

“I was viciously attacked by Mr. Khan at the Democratic Convention. Am I not allowed to respond?” the Republican nominee for president asked in a tweet.

Khizr and wife Ghazala Khan, the parents of a slain Muslim soldier, offered a powerful rebuke to Trump on the final night of the DNC.

In an eight-minute speech, delivered by Khizr, the family questioned whether the New York businessman had ever read the US Constitution or sacrificed anything for his country.

Trump hit back on Saturday, suggesting Ghazala was not permitted to speak because of her Muslim religion. The billionaire further argued that he had indeed sacrificed for his country, saying he created jobs.

Trump’s remarks were widely condemned and the billionaire eventually began walking them back. In a Saturday night statement, he called the Khan’s son a “hero to our country” and tried to shift the issue to “the real problem” which he argued was “the radical Islamic terrorists who killed him.”

Khizr Khan said Sunday that Trump's questions about his wife represent the "height of ignorance."

Ghazala Khan also wrote an op-ed in The Washington Post saying she didn’t speak at the DNC because she finds it too painful to think about her son.

“Without saying a thing, all the world, all America, felt my pain,” she wrote.