FBI Director James Comey testified before the House Committee on Homeland Security, on October 21, 2015, that we cannot properly vet Syrian refugees.  Comey said:

We can only query against that which we have collected.

And so if someone has never made a ripple in the pond in Syria in a way that would get their identity or their interest reflected in our database, we can query our database until the cows come home, but there will be nothing show up because we have no record of them.

According to the Daily Caller article, supra:

More than 4 million Syrians have fled their homeland amid a brutal civil war. But many Middle Eastern countries have refused to accept refugees, putting the burden on Europe and the West.

Comey is correct that we cannot properly vet Syrian refugees or refugees from other Middle East countries.  The typical vetting would involve researching public records, police records, and court records; interviewing friends, neighbors, and acquaintances of the refugee; and interviewing with the refugee.  Comey said these records do not exist, so we are left with just interviewing a refugee and accepting what he tells us.

There is no evidence that the situation has changed since Comey's testimony of October 21, 2015, nor is there any evidence from responsible authorities to contradict Comey.

Former National Intelligence director James Clapper said in September 2015:

I don't, obviously, put it past the likes of ISIL to infiltrate operatives among these refugees, so that's a huge concern of ours[.]

The WikiLeaks release of Hilllary emails shows that Hillary said in 2013 that the country of Jordan "can't possibly vet all those Syrian refugees … so they don't know if … jihadists are coming in along with legitimate refugees."

Obama appointees Comey and Clapper, responsible for vetting refugees, expressed doubt about properly vetting such refugees.  It logically follows that if we cannot properly vet the refugees, then Trump's directive for a temporary ban on allowing refugees into our country so we can review the vetting procedures for the seven designated countries is reasonable and in the interest of protecting Americans.

The background of this refugee problem is the Syrian Civil War that started in 2011.  Syria has a population of about 22 million, with demographics of 60% Sunni Muslim, 10% Christian, 11% Shiite-Alawite, 9% Kurd, 3% Druze, and others. 

From this we can assume that most of the refugees are Muslim.  As of December 2015, only 3% of the Syrian refugees to the USA were Christians.

Russia, Iran, and Hezb'allah support Assad, a Shiite-Alawaite.  Turkey, USA, and others supported the rebels who started fighting Assad in  2011.

Complicating the war is that ISIS joined the fight against Assad, which increased the brutality of the war and the number of refugees.  Obviously, the interests of the USA and ISIS differ, but we were on the same side fighting Assad.  It is difficult to tell the good guys, if any, from the bad guys.  For example, in 2013, U.S.-supported "rebels" massacred 45 Christians and destroyed 14 churches in Sadat, Syria, while shouting, "Allahu akbar."  And in August 2014, an al-Qaeda group attacked the Christian town of Maaloula and were beaten back by Assad's forces, aided by Hezb'allah. 

But the opposition party acts as if the victims were only Muslims and as if vetting refugees were somehow anti-Muslim. 

The war is bad guys against very bad guys.  We opposed Iran in Syria at the same time that Obama was negotiating the nuclear deal that gave Iran 150 billion dollars, which it used to finance Hezb'allah. 

Obama threatened Assad if he used chemical weapons, but Obama did not follow through, as demanded by war hawks such as John McCain.  Obama stumbled into the correct policy of not bombing Assad because the removal of Assad would further destabilize Syria, which would lead to ISIS gaining more control as it did in Libya and Iraq.  This would have caused more refugees, especially Christian refugees as in Iraq.

Unfortunately, the choice in Syria is between Assad, a thug, and ISIS, a murderous group that supports terrorism in Europe and the USA.  From this mix of Hezb;allah, ISIS, al-Qaeda, and others, how do you vet refugees who want to leave Syria?

Even by raising these facts, the opposition party (Democrats/MSM)

blathers that we cannot consider the background and religion of the refugees because this would be un-American.  The first American value is to protect Americans, not to allow in refugees who have not been properly vetted.

We do not know if the vetting process questions the refugees on whether, as Muslims, they believe in sharia law, and whether it should be applied in the USA.  Since ISIS is in Syria, its members can easily infiltrate the refugee camps, as Comey and Clapper said.

There should be a thorough evaluation of the vetting procedures and the history of the refugees who have been settled in our country and in Europe.  The Obama political appointees should all be removed, and the investigation and evaluation must be done by professionals with the first priority to protect our country.

There is no evidence that the situation has changed since Comey's and Clapper's statements.  There is no assurance that ISIS is not infiltrating terrorists among the refugees.  There is no assurance that the refugees do not have terrorists in their midst.

Even if one terrorist infiltrates, that will result in deaths and injuries for Americans.  The speeches by the opposition party of the Democrats and MSM, coupled with Madonna's testimony, are not evidence that the facts and analysis set forth by Comey and Clapper have changed. 

The opposition party are more concerned with using the refugee issue to attack President Trump than with the safety of the United States.