Well, there is a hidden externality here. Traditionally helpesk and tester roles have been a "feeder" for sysadmin and developer roles. They are entry level jobs that are easier to get, a company gets to see who is talented and ambitions and they "move up" to more complex and technical work. If that pipeline disappears because helpdesk and testing have moved offshore, then the Western IT firms lose the ability to hire capable people that for whatever reason haven't gone the CS degree route, and those people lose the opportunity to get into the industry too.
Actually, IT labour is not cheap in India. It is quite common for IT workers to expect 15% minimum yearly increase in salaries and not less than 30% hike in salaries when switching jobs.
The Rupee-Dollar arbitrage is the biggest advantage Indian IT companies are enjoying right now.
That is exactly the point. Why resort to protectionism. Let the market forces play themselves out. Protectionism is just the opposite of what the US preached to the world.
Indians are sufficiently entrepreneurial - especially given the constraints they work under. I am quite confident that Indians would figure out a model that will continue to work.
When India is really up to the standards of the US, it's not going to be cheap anymore.