Certainly not 2 million. It would be really difficult to tell, actually. In villages a person can declare himself to be almost any religion, suitable to the moment. When I travelled in India, taxi drivers, or tuktuk drivers would change their religion based on which religion their passenger was, hoping for a better tip, or a tip at all. Off in some remote village, it's really hard to say. For survival, or because of literacy or language issues, anything can be said. Lots of village Hindus, not knowing the difference, will say they are members of all religions. It's an easy answer, supposedly won't insult anyone.
I seriously doubt if there are more than 20 000 active Baha'is in India. They might be active on every 19th day to get something to eat, but then stay with Hinduism the other 18 days. Is that really an active Baha'i? If they're still practicing 'idol' worship, are they Baha'is? But you're free to differ. I am glad you didn't claim it was 2 million.
I've also looked at many large Indian cities on google map, and very few have Baha' Centers anywhere. Again, you're free to differ.