What were non-Communist contemporary reactions to Stalin's purges?

The show trials of the 1936 to 1938 period were widely denounced throughout western Europe and the United States. There was formed an international inquiry to exonerate Trotsky, sometimes called the "Dewey Commission." This board made highly publicized reports documenting the falsification of the evidence and unsubstantiated allegations made in the Vyshinsky prosecution. Counter-Stalinist responses were given wide publicity, not just as editorials, but as news. For example, when Trotsky wrote an open letter from exile in Norway claiming that Lenin's widow privately denounced Stalin as "without honor" and immoral, this was widely published as news.

In the United States, although some public leaders like Roosevelt and his followers made no statements against Stalin, many others routinely condemned both the murderous policies of Stalin against the Soviet people, and his vicious oppression of opposition to his rule. For example, in 1938 Herbert Hoover, the former president, gave a speech the theme of which was the following:

A score of democracies have sunk since the war and armed dictatorships have risen in their place. They proclaim new ideologies of economic security to sanctify their personal power. They live by terror and brutality. -- Herbert Hoover, in Toronto, November 22, 1938

Wide publicity was given to anti-Stalinist figures such as Alexander Kerensky, the former chair of the Russian provisional government, who spoke frequently in front of gatherings and crowds. In one interview in 1938 he said:

The common hatred of Stalin is tremendous... his game is contradictory and hopeless. He seeks to divert the wrath of the Russian people from himself by branding all the other Bolshevik leaders as traitors. [It should be obvious to all] including even the most ardent apologists for Bolshevism, [that what we are now witnessing] is the moral bankruptcy of Bolshevism."

-- Alexander Kerensky, New York City, March 3, 1938

In general, the purge trials were met with disbelief in the west and characterized as biased and politically motivated.

The answer of Tyler Durden is essentially correct but somewhat one-sided. So let me add that there was an influential part of population, which cannot be called "communist" in any sense, and which approved Stalin's policies in general and mock trials in particular. I mean some intellectuals, and there were many. And they were influential. Bernard Shaw. Romain Roland. Lion Feuchtanger, to name just a few.

Lion Feuchtwanger, an outstanding novelist traveled to Soviet Union, and was present at the trials. After that he wrote a book "Moscow, 1937" with a complete approval of Stalin and the trials.

Later Feuchtwanger tried to justify himself by saying that he saw the greatest danger in Hitler, and could see only in Stalin a counterweight to Hitler. Therefore he supported Stalin. So for Feuchtwanger this was a kind of "trade with his conscience and moral principles".

This was a popular way of thinking among the intellectuals at that time, as I understand.

But bribing Western intellectuals, especially the popular writers was also done by the Soviet government on a grand scale. And this did not have to be a direct bribing. One way was paying royalties for the books of some authors whose translations were printed in millions copies in Soviet Union. (Book publishing n Soviet union was apparently heavily subsidized, and the books were very cheap, so circulation of some authors really reached millions).

(I am NOT talking here on Communist artists and authors of which there were also very many, and certainly they had large influence, not only among communists).