I am not a supporter of Donald Trump, but when the Pope comes to the US-Mexican border and says that anyone (meaning Donald Trump) who builds a (border) wall instead of bridges is not a Christian, he is out of line.
I have no doubt that Pope Francis I is a decent man who cares deeply about the plight of the poor. He has proven that over the course of his life. he also seems to want to cut down on the opulence of the Vatican. That is also a noble goal. But he has no business telling us that we cannot build a wall to guard our border. He also has no business casting judgement on Trump's faith. (Trump is a Presbyterian.)
We'll see how the Pope feels about this subject when all those migrants, refugees and jihadists start storming the Vatican and St Peter's Cathedral.
PS: Don't tell my wife I'm writing this. She's a Catholic and loves Francis.