Is Building a Wall always a bad idea?

I am not clearly set in regards to how I feel about a wall being built but I can see some inconsistent thinking coming from some who oppose the idea, especially when they try to say it is universally wrong to do so from a Christian perspective.

Enter the Pope as he says that anyone who wants to build a wall "is not Christian".

His way of thinking would actually be in line with the neighboring Kings in Nehemiah's time who ridiculed Nehemiah for wanting to rebuild the wall around Jerusalem. No doubt they feared that the wall would bring the necessary safety for the Jewish people to once again flourish and grow strong thus threatening their own power and control in the area.

But when Sanballat the Horonite, and Tobiah the servant, the Ammonite, and Geshem the Arabian, heard it, they laughed us to scorn, and despised us, and said, What is this thing that ye do? will ye rebel against the king? Nehemiah 2:19

But it came to pass, that when Sanballat heard that we builded the wall, he was wroth, and took great indignation, and mocked the Jews. And he spake before his brethren and the army of Samaria, and said, What do these feeble Jews? will they fortify themselves? will they sacrifice? will they make an end in a day? will they revive the stones out of the heaps of the rubbish which are burned? Now Tobiah the Ammonite was by him, and he said, Even that which they build, if a fox go up, he shall even break down their stone wall...But it came to pass, that when Sanballat, and Tobiah, and the Arabians, and the Ammonites, and the Ashdodites, heard that the walls of Jerusalem were made up, and that the breaches began to be stopped, then they were very wroth, And conspired all of them together to come and to fight against Jerusalem, and to hinder it.Nehemiah 4:1-3, 7-8

There certainly did not seem to be an issue with walls for the sake of defense during Nehemiah's time.

And I said unto them, Let not the gates of Jerusalem be opened until the sun be hot; and while they stand by, let them shut the doors, and bar them: and appoint watches of the inhabitants of Jerusalem, every one in his watch, and every one to be over against his house. Nehemiah 7:3