The point of the Summons etc is to drive a wedge between US and India: the targets are the binjnejes. So no point in walking into that trap with a lot of tit-for-tit childishness. HOWEVER, well-targeted actions are needed, which is what I listed.
Reply to the offending Judge, asking him/her/it to get a grip on the law and demand dismissal with costs. If they don't dismiss, THEN slap the US system for obvious refusal to abide by even US law.
If they dismiss, Hizzoner is still going to have a clear imprint, posteriorously impressed. Other judges will see it and
File a countersuit in the name of Indian voters (and since there have to be Offended US Parties, in the name of 1 million desi-Americans. File it for a sum like 330M (OK< make it 331M). Cite the slander and real and punitive damages. Publicize that fact.
Force Discovery - exactly who was behind the idiot suit. Publish far and wide: you would be surprised. I bet it's the Baptist conversion scams. The ones really behind these need to be exposed.
Publish that widely in India.
File Contempt of Court charges in India.
Declare all those persona non grata in India. Close their outfits in India, ban their businesses.
That way their support base in the US will feel the real pinch and the pain-in-da-butt.
This cannot be left to the Indian babucracy, esp. the Indian Embassy and Conjulates. All useless. They probably haven't even woken up to read the news.
There is no need for nonsense tit-for-tit stuff in India - Indian courts won't issue any such Summons which go against international law. But Indian courts have smart people too: they WILL go after these buggers for contempt. Look at what they did even to the DRDO mandarins. Even Arundhoti got Contempt of Court slapped on her, and had to go (never mind) someone to "get off".
The CAPEEM ppl in California, on barely a shoestring and prayer, kicked the butts of the entire California Ejjukashun Bored and the might of HahVahd's Foundation Lawyers and Don "Quixote' Witzel, reducing the latter to a whining lump of jelly in the Discovery process.
Surely all the might of the desis now assembled in Noo Yoik can do better than that? Have to convey some serious lessons.