This is a really unnecessarily rude way to call out a minor grammar quibble. The sentence was perfectly understandable. Also, whether you like it or not, it is quite common English (at least in the US) these days to use they/them as third person singular. Perhaps we are slowly losing the distinction between singular and plural the same way we lost it for second person. Language changes.
GP is obviously using "them" to refer to the formulas. I understand how it could be confusing; on first pass I too looked back for the first word "them" could be referencing - but GP tricks us by writing out "god" again later in the sentence! Since we know Ramanujan is male and "god" is used again, the only valid noun "them" could be referencing is "formulas".
Since Ramanujan is dead, I assumed that he had no interest in arguing with the man and was instead talking about anyone with such inspiration.
As an English grammar stickler, of course thou should have said "Why art thou" since the use of "you" in the singular is simply grammatical hooliganism and has no place in polite society.
