Priya: Listen, Rajesh, Leonard and I have decided to see each other again, and you don’t get to tell me who I can and can’t have a relationship with.
Sheldon: Actually, he can. The Hindu Code of Manu is very clear in these matters. If a woman's father is not around, the duty of controlling her base desires falls to the closest male member of her family; in this case, Raj. The code also states that if she disobeys, she will be reborn in the womb of a jackal and tormented by diseases. If true, that seems like an awfully large gamble given that the prize is Leonard.
Raj: There it is, Priya. We're Indian. We believe this stuff.
Priya: I think it also says that if you eat beef, you need to live with cows for three months and drink their urine.
Raj: Some of it makes sense, some of it's crazy. My point is, you can't go out with Leonard.
"Some of it makes sense, some of it's crazy" is basically the response I got recently when (with great foolishness) I ventured to say on an online forum that it isn't wise to cite the Bible as a defense for being anti-gay, since you could also use the Bible to be pro-slavery and pro-stoning-women-to-death-for-adultery,
The Big Bang Theory is comedy. They know Raj is actually objecting to his friend dating his sister because of a basic annoyance and disgust factor, not really because of religion. Religion is just a handy excuse. So, yeah. Parallel, much?