Queer was a human epithet for homosexuality.
In 2009, Clement McDonald called Ianto Jones a queer, saying that he "could smell it." Ianto objected, implying through the phrase, "This isn't 1965" that the word was old-fashioned and no longer appropriate in the 21st century. (TV: Children of Earth: Day Three)
Behind the scenes
Queer is a reclaimed term which functions as an umbrella for various sexual and gender minorities. For context on Ianto's comment, its use as a derogatory term was indeed at its height in the 1960s, before those in the LGBTQ community reappropriated the word queer in the late eighties, as a mark of pride.