Were his methods ethical? Shit no! Very few fucks were given about his subjects' consent -- which is ironic, considering the many levels of fucking otherwise involved in the study. However, here's the absolute craziest part about Humphreys' study: It worked. Not in a "earned the dude scores of grants and accolades" way -- although the Tearoom Trade study remains a scientific landmark, that's mainly because it's a textbook example of unethical social research. No, the study actually yielded positive results for the gay community.
Plot twist, motherfuckers!
Before Humphreys' study, the public opinion about men participating in public gay shenanigans held that they were dangerous social and sexual deviants. The study revealed that they were mostly regular folks and upstanding citizens. In fact, the majority of them were regular family men who, due to the attitudes of the era, had no other outlet to this side of their sexuality. Though this presumably opened a whole new can of worms of the "Hold on, you told me you were working overtime" nature, the gay community by and large welcomed the study. Hell, even the 1960s police found itself putting one foot in the "gays are people, too" bandwagon (sort of), as many precincts realized the tearoom trade was a victimless "crime" and stopped actively stomping on the people practicing it, instead focusing on being the tolerant and fair organization we know the police as today.