Donald John Trump Jr. nailed it.

He posted this message via Twitter: “You know why you can enjoy a day at the zoo? Because walls work.”

Where do I begin? I’ll start with this: Don Jr. has issued — hands down! — the most preposterous argument yet in this discussion over whether to erect The Wall along our southern border.

He has, in the minds of many critics, compared illegal immigrants to lions, tigers and bears . . . oh, my! Yep. If we’re going to build walls that separate zoo visitors from vicious animals then we should do precisely the same thing to keep illegal immigrants from entering the United States of America.

I thought that Don Jr.’s dad’s assertion that movie stars, politicians (including former presidents) and the pope living behind walls took the cake for bodacious rationalization. I was wrong. The eldest son of the president has won the take-the-cake prize.

Should we care about what a president’s son has to say about this? In most cases, no. This fellow, though, has become a spokesman of sorts for the president of the United States. He pops off randomly to make some kind of point. He’s usually off base, but what the heck? He carries the name of the man elected to lead the world’s most indispensable nation. That, by itself, seems to lend a bit of misplaced gravitas to the idiocy that sometimes flies out of his mouth.

Illegal immigrants are not wild animals. They are human beings. They aren’t all scurrilous criminals. Most of them are seeking a better life for themselves and their loved ones. Indeed, most illegal immigrants are here legally already, but who have remained past the time their work visas have expired.

Donald Trump Jr. lends not a single constructive thing to this debate. However, his nonsense is worth a brief comment here because — dare I suggest it — he well might be echoing the views of his father.

Disgusting.