Sorry, but that's just flat out wrong. That's the old "Smoot-Hawley" canard, which has been disproven about a thousand times now, but that doesn't keep the free trade uber alles crowd from repeating it over and over again!
If you want a real education about the actual causes of the Great Depression, just google up the phrase "great myths of the great depression", which is an article posted at the mackinac institute, and written by Lawrence W. Reed.
I am just so tired of the same old "Smoot-Hawley" argument being hauled out time and time again. It is wrong, and it needs to be done away with forever. It's the economic equivalent of claiming the world is flat, it's just utter nonsense.
Your own source blames Smoot-Hawley, in large part, for the Great Depression.
The crowning folly of the Hoover administration was the Smoot-Hawley Tariff, passed in June 1930. It came on top of the Fordney-McCumber Tariff of 1922, which had already put American agriculture in a tailspin during the preceding decade. The most protectionist legislation in U. S. history, Smoot-Hawley virtually closed the borders to foreign goods and ignited a vicious international trade war.
...
Officials in the administration and in Congress believed that raising trade barriers would force Americans to buy more goods made at home, which would solve the nagging unemployment problem. But they ignored an important principle of international commerce: Trade is ultimately a two-way street; if foreigners cannot sell their goods here, then they cannot earn the dollars they need to buy here. Or, to put it another way, government cannot shut off imports without simultaneously shutting off exports
Just get used to it . . . imagine how a "free-trader" feels whenever somebody trots-out that Karl Marx quote.