Franklin Graham, one of America's most prominent faith leaders, has called out President Obama for continually defending Islam in the face of criticism, but staying silent when Christianity comes under attack.

In an open letter shared on his Facebook page, Graham, the leader of Samaritan's Purse, pointed to where the President criticized presumptive Republican presidential nominee Donald Trump for proposing a ban on Muslim immigrants in the aftermath of the shooting massacre in Orlando.

"A Muslim can murder 49 innocent people in a gay club, and you still defend the religion of Islam," the 64-year-old evangelist wrote. "But a Christian who refuses to bake a homosexual's wedding cake endures prosecution, financial ruin, and nation-wide shaming because of their faith, and you stay silent!"

On Sunday, 29-year-old Omar Mateen, who had pledged his allegiance to the Islamic State terror group, opened fire at a gay nightclub in Orlando, killing at least 49 and wounding dozens of others. In response, Trump suggested that all Muslim immigrants posed a threat to American security and said that while Obama claims "to know our enemy," he continually prioritizes "our enemy over our allies and, for that matter, the American people."

The President in turn accused the GOP frontrunner of peddling a "dangerous" mind-set that "singles out immigrants and suggests entire religious communities are complicit in violence."

"Where does this stop?" Obama said of Trump's approach. "Are we going to start treating all Muslim-Americans differently? Are we going to start subjecting them to special surveillance? Are we going to start discriminating against them because of their faith?"

Mateen reportedly drove several hours from his home in Port St. Lucie, Florida, to the gay bar early Sunday and, armed with a rifle and a handgun, shot more than 100. Mateen, who was carrying a handgun and a Sig Sauer MCX, died in a shootout with police following what is now recognized as the worst mass shooting in modern U.S. history, and the most deadly act of terror in the country since 9/11.

Twenty-seven victims remained hospitalized Tuesday. Six were in critical condition, according to hospital officials who said the death toll was still at risk of rising because one or two of those patients were "profoundly ill."

Continuing his Facebook comment, Graham emphasized that "what Omar Mateen did was following the teachings of the Koran."

"It is incomprehensible that you will not acknowledge the dangers of Islam's teachings in order to protect the American people under your watch," the evangelist said.

Mateen was investigated by the FBI back in 2013 after making "inflammatory comments" to co-workers alleging possible "terrorist ties."

The following year, the FBI investigated him once again because of ties with an American who traveled to the Middle East to become a suicide bomber.

Law enforcement sources told NBC News he swore allegiance to the leader of the Islamic State group, Abu Bakr al-Baghdadi, in a 911 call made 20 minutes before the rampage at Pulse. He also reportedly mentioned the Boston Marathon bombers, a U.S. official said.

Earlier, Graham criticized Obama for refusing to call the Orlando massacre an act of "radical Islamic terrorism" and urged the President to "wake up" to the threat currently facing the nation. 

"I appreciate President Barack Obama speaking to the nation yesterday in the wake of the Orlando massacre. He was right in saying that this tragic shooting was an act of terror and hate," Graham wrote.

"But why didn't he say it was an act of radical Islamic terrorism?"

He added, "Mr. President, with all due respect, don't forget Fort Hood; don't forget the Boston Marathon; don't forget San Bernardino; and don't forget 9/11. What do they all have in common? They were all Islamic terrorists carrying out their treachery in the name of their religion."

"Mr. President, your administration has cut our military to the bone and some experts say we're the weakest we have been in modern times. It's time we were rebuilding our military force worldwide to take on this enemy," the evangelist continued. "It's time we tighten America's borders until we can clearly vet those we're letting into the country."

"Mr. President, how many more American lives have to be lost before you understand the threat radical Islam is to every freedom-loving person?" he asked.