Assume you are the defendant and you are innocent. What would you do?
A. Spend a million for defense.
B. Default.
C. produce the birth certificate right away and show us for the fools we are, save money, and get about your business.
Didn’t someone try to disqualify Dick Cheney in 1992 claiming he was really a resident of Texas, not Wyoming, and therefore ineligible to serve as VP since Constitution says Pres and VP must be residents/citizens of different States? I am sure this happened and think he defended in the same way.
There are lots of tactical ways to fight a lawsuit. Sometimes it is advantageous to move to dismiss rather than respond to the claim.