First of all understand his legacy.
Bal Thakrey has become what he has(not that he is as powerful as he was say 10 years back) by the politics of hate, extremism and related. The root of the existence of that party is based on Marathi pride(whatever that is). For starters i think those who talk of such matters reflect their own weakness. But everywhere this issue has happened, its a political stunt to wrest power. The whole Khalistan moment is based on the same premise. At the end of the day its the politicians who make the people believe that its good for them if the went ahead and did what they are saying.

That brings me to the next point. Its very important to understand the mindset of the supporters. There arre two types of supporters. One are the blind ones, and usually the handful ones. They won't see any logic, they have no conscience and they will basically go ahead and do what their leader said. There is very little one can do about these fellows apart from putting them in jail. The pother group of supporters are the common folks(again there can be different levels of extremist mindsets one can see in them also, but the basic typecasting is that they are driven by some logic, or they associate themselves with some point or issue that the politician has raised.

I think if you look at Shiv Sena and to a lesser extent Raj Thakrey, they have had a sizeable number of supporters of the latter type. There is a group(and thats the lower income marathis, lets say small vendors, rickshaw and taxi drivers, the vegetable sellers) who feel that their jobs have been lost due to the influx of people from Bihar, UP and other places. That this is their state but people from other state(who might be more aggressive) are taking over their livelihood.The most obvious counter to that is why don't the Marathi's go to other places also to do that. That however does not take into account that in India there are different kinds of people in every state. Some are humble, calm; while others might be enterprising; while still others are aggressive and hard working.(They are bound to be deviations and anomalies, a class is never same but this is a general class statement) The reason for this group being what it is, is basically due to the conditions that existed at places they have lived for ages. So if Punjab has had the most fertile lands, people have always been rich. They have had the money to think big and start own businesses. Cut to Bihar where modern India has never looked at lifting that state, you have utter chaos and lawlessness. Once you are in a country, the people who feel deprived, who see better opportunities elsewhere will always look to try their luck there. Restrictions here would question the meaning of India as a whole. (We already know that restrictions in Kashmir to settlement by article 372 haven't helped that state become any better)

You could have avoided most of these issues if you never split the country on linguistic lines, but that's not something we can change. The mindset of this is our place and no one else's is also a weak man's mindset. The inability to compete with the rest(a very good argument world over against globalization) but inspite of that the only way to tackle this issue is development. If you were to give the Bihari's proper working opportunities in their own state, much of the sensitive lower income exodus would stop. These are the group of people that's exploited by the politicians. I think contrary to what Raj is saying, which is plain rhetoric as he cannot bring the issue into attention of the media without targeting some elite, this is not at all about the elite. This is about the lowest strata of society in Maharashtra, particularly in and around Mumbai who think that the influx of people from other states is taking opportunities they finally have to rise up. There is also a feeling that such people bring in customs(and i mean the bad ones) that degrade the existing practices that were being followed by the natives(no one looks at what good they brought, its the old saying, you notice and absorb the bad things faster than anything good). Plus the people who come might be desperate(they are for if they weren't they won't have come anyway)and they might be willing to do anti social, non honest dealings to survive which the natives might not(for anything right from finding a house to a job in the new place). There is some sense in what the natives say. But then Metros are like that world over.

So while we all should stand up against what the guy is trying to do, also look at the basic underlying issue that his party has raised. I for one believe that the way our country is, its important that equitable growth takes places. The problems of non-equitable growth lead to bigger issues that would rake up even bigger problems that would be very tough to control. Its not about who you are or if this is against your community, its about objective analysis and finding out how this issue at its heart can be tackled.

(ps: There is no substitute for development. India cannot progress without Bihar and UP progressing. Would the politicians allow that though is an open question.)