Re: STID and the Eugenics Wars books
^The question isn't about what the basis for Marla's deduction was, the question is whether the episode itself established Khan as a Sikh in dialogue. And it did so in two ways: one, by having Marla state it outright, and two, by giving him the surname Singh.
But do only Sikh men have the last name of Singh?
I know we had a Lieutenant Singh in Lonely Among Us
"Just give me two seconds, alright, you mad bastard!" - Montgomery Scott, Star Trek Into Darkness