Do you seriously think that they had 15GB of email? It's a pretty small email provider that doesn't support much space and filters. I think "entire" and "filled" are most likely examples of exaggeration, not facts.
Was it really "Bangalore and Hyderabad"? They had it in the signature of the email? They did a statistical analysis on where they came from? None were from Eastern Europe, Japan, the US, England, or college students? Most English native speakers I know have horrible written communication skills. This is also most likely exaggeration, not facts. Even if you traced the IPs of the messages you would still not be able to claim location, we all know how IPs do not correspond 1:1 to physical people.
He knows that they were doing it because they were outsourced to? They stated that in their questions? I would love to see some evidence of this. Even if they did "fill" his inbox, with messages truthfully stating they were from Hyderabad and Bangalore, they also told him that it was work that was outsourced to them? I doubt that is even exaggeration for effect.
I would like to see this 15GB archive of email showing that proves this is true. Either that, or it seems to be a gross generalization targeted at a specific race or group of people. Which isn't just racist to people who have fallen victim to over sensitivity in service of political correctness.
They then go backwards to post-rationalize and assign reasoning/causation in order to 'explain' the discrepancy. "Well, 20% of all developers are of minority A, therefore they are not fairly represented if there are only 5% of them using this library."
You've probably heard this before, but correlation is far from causation.