Re: Can India stay united as a nation if Hindi people are asked to leave Maharashtra?
I don't know if I consider that to be a very apt analogy.
It sounds like the problem is the exact opposite; in Karachi, the Mohajirs were resented because they were largely a educated, bourgeois population that edged out the locals in competition for skilled, middle class jobs...a 'market dominant minority' if you will, similar to (but not quite to the same extant as) the Indians in Kenya, or the Chinese in the Philippines. It sounds like the problem in Bombay is rather different; the Biharis are poor and uneducated, and are coming in and (cheaply) filling the unskilled labor forces...like Central American migrants in the US (but legally)...
The similarity is that Urdu replaced Sindhi as the language of Karachi. Similar thing is happening in Mumbai and rest of Maharashtra. Marathi is being replaced by Hindi. Hindi speakers do not attempt to learn Marathi.