Anyone who studies or follows economics knows that S-H made matters worse, so when you see that argument it comes from someone who doesn't understand the facts, whether it comes from a "free-trader," or a "protectionist" using it as a red herring. (In my experience, the latter is more often the case).
It can be argued that S-H made it worse, but not a) how much (because there were so many other things happening at the time, with insufficient data collection, so there is little way to tease out effects of S-H by itself), b) for how long, or c) what lasting effects it had, since many of the trading partners who complained the loudest about S-H had far more pressing issues to complain about in a few years’ time.
The point is that the “free trade” crowd hasn’t seen their agenda stand up to the facts and data collected during this downturn. Trade has fallen faster now that we have “free-er” trade than in the Depression, so free[er] trade doesn’t stop, nor even slows down, the effects of a credit collapse, and putting in this tire tariff isn’t likely to produce results as GOOD as those under Smoot-Hawley.
In short, for those worrying about a trade war now: stop worrying. We had better trade stats in the 30’s during the S-H trade war than we have now.