Donald Trump asks: Why would I defend Obama against claims that he's a Muslim?

US Republican presidential candidate Donald Trump holds his Bible while speaking at the Iowa Faith and Freedom Coalition Forum in Des Moines, Iowa, on Sept. 19, 2015.Reuters

During a question-and-answer town hall event in Rochester, New Hampshire, last week where Republican presidential hopeful Donald Trump was the invited guest, an unidentified man made controversial remarks against US President Barack Obama.

"We have a problem in this country. It's called Muslims. You know our current president is one. You know he's not even an American," said the man, adding that he wanted to "get rid" of Muslims in the US.

In response, Trump chuckled and simply said, "We need this question. This is the first question."

This incident caused the business tycoon to draw criticism for not correcting the claims made by the unidentified man against Obama.

On Saturday, Trump took to Twitter to defend his silence on the accusations against Obama.

"Am I morally obligated to defend the president every time somebody says something bad or controversial about him [Obama]? I don't think so!" Trump said in a tweet.

"This is the first time in my life that I have caused controversy by NOT saying something," he added.

The Republican presidential frontrunner further pointed out that Obama would not have defended him if placed in the same situation.

"If someone made a nasty or controversial statement about me to the president, do you really think he would come to my rescue? No chance!" Trump said.

He also said that he would have been accused of curtailing freedom of speech if he corrected or rebutted the man who made the controversial remarks against Obama.

"If I would have challenged the man, the media would have accused me of interfering with that man's right of free speech. A no-win situation!" Trump tweeted.

White House spokesman Josh Earnest, meanwhile, said he was no longer surprised about Trump's inaction towards the criticisms against Obama.

"Is anyone really surprised that this happened at a Donald Trump rally? The people who hold these offensive views are part of Mr. Trump's base," Earnest said during a briefing.