Hiya
I'm not sure it's the right question - because I'm not sure that God's Spirit was ever with the ORGANISATION. I do think that the Spirit is with INDIVIDUALS within the organisation.
As for your friends answer, that's typical of JW flawed thinking.
0% increase indicates withdrawal of the Spirit? Therefore growth indicates Spirit is with them. So if the Catholic church shows growth this is evidence of God's Spirit?
By your friends' reasoning all other religions should have fizzled out by now.
For me it's this whole ORGANISATION thing which is the biggest red herring going. Constantly looking for the One True Organisation.
I feel that the ONLY logical conclusion I've ever been able to reach, after everything I've discovered about the WT is that they cannot be God's EXCLUSIVE channel. However I don't feel that I could say that God has NEVER used the organisation or doesn't approve of sincere individuals.
One thing I do believe that God has done is make information about the WT (and anyone else for that matter) freely available.
So slightly different question and answer:
Q. If God wanted to show us that the WT was not his Exclusive Channel how might he do it?
A. By making information about the WT freely available to all. (?)
"and God said "let there be the internet . . . and there was the internet"