(CNN) Shortly after Pope Francis called Donald Trump's plan to build a wall on the U.S.-Mexican border "not Christian," the GOP front-runner's campaign was ready with a response:
Isn't Vatican City, the Catholic Church's 110-acre sovereign state, surrounded by walls?
"Amazing comments from the Pope -- considering Vatican City is 100% surrounded by massive walls," tweeted Dan Scavino, the Trump campaign's director of social media and a senior adviser.
That's not quite true, though, said several Catholics familiar with the layout at Vatican City.
Yes, the Vatican does have walls, and some are quite large. But anyone can stroll through the Pope's front yard -- St. Peter's Square -- at nearly any time. Only metal detectors stand between the iconic landmark and the millions of tourists who come to see the historic headquarters of the Roman Catholic Church.
In other words, Vatican City may have walls, but the front door is always open, said the Rev. James Martin, a Catholic priest and editor at large at America magazine.
The Pope, 'the Donald,' and the wall between them
"The fortifications were built a very long time ago," Martin said. "This Pope didn't build them -- and he certainly didn't build them to keep out poor migrants.
To emphasize his point, Martin tweeted a picture of St. Peter's Square.
CNN religion analyst the Rev. Edward Beck likewise took to social media to counter the Trump campaign's arguments. The walls were built in the 800s to protect the pope from barbarian invasions, Beck said.
So the Pope's walls may not be that impressive -- but his political clout apparently is. His comments on Trump dominated the news cycle on Thursday.
But Trump fired back.
"No leader, especially a religious leader, should have the right to question another man's religion or faith," Trump said, calling the Pope's remarks "disgraceful."