We have studied the Great Wall of China and the Berlin Wall in history.
The first was built to defend the border of the territories, the second was built for political reasons.
We cannot connect Trump's wall with the latter because the former were built for justified reasons, instead Trump's wall was built for senseless reasons, or to divide the United States of Mexico.
Anyway building walls to defend oneself or to attack, for me, is wrong.
The walls are built only when houses have to be built, in which many families can live, and not to create divisions that cause many hardships, impoverishing the world.