"Is the fact that he loudly expressed our own disgust with the political establishment a sufficient reason to gamble the whole future of the country by putting him in the White House?"
This remains the essential question.
Sowell, in the rest of the article, does not answer this, and gives no alternative as to why we should vote for anyone else who is unwilling to express disgust with the political establishment. His descriptions in the rest of the article basically said that there is no one worth voting for.
Actually, his entire commentary is an answer to the above question. Sowell makes the following points: character matters (Trump doesn't have it.). Experience matters (Trump doesn't have it). Maturity matters. Trump doesn't have it. Trump aided and abetted Obama. Trump is a messianic demagogue not unlike Jim Jones or Hitler. And finally, Trump is unelectable nationally.
All of these points, and others, were made by Sowell---all responsive to the question you quoted above---it's not enough merely to express disgust with the government.
Jordan