Andrew and Jonathan wandered off from the caller's main question, so I want to make a few points.
First, I take exception to his premise that immigrant workers are willing to work for less. Anyone who works and lives in the US faces the same housing costs, the same transportation costs, the same food costs and the same consumer culture telling us to buy, buy, buy. There's no reason an immigrant worker would be able or willing to work for less than a citizen. Unless... immigrants jobs are by definition more precarious. The HB-1 visa is tied to the "sponsoring employer". Although it is possible to transfer to a new sponsoring employer, this is a bureaucratic hurdle not present for citizens looking for new and better positions. HB-1 workers are also far more vulnerable to unemployment as they may lose their visa status. This encourages them to take the first available job rather than hold out for better wages and conditions. There may be other issues as well. When a significant fraction of the workforce is more exploitable it holds down wages for everyone. But the answer is not to restrict the number of immigrant workers, but rather to reform the visa rules to ensure that immigrant workers are able to demand equal wages.
Second, it is sometimes argued that even if immigrant workers are not different from citizens, having a larger pool of IT labor available suppresses wages for IT workers. This may be true, but only if the market for IT services is saturated. If there is still potential untapped demand in the IT industry, increasing the labor pool will simply allow existing firms to expand and new firms to form, increasing demand for IT labor along with supply. There may even be multiplier effects where expansion in one firm creates new demand and new jobs for subsidiary services. Conditions vary based on the overall economic climate and the maturity of the specific industry, but often increasing the workforce increases the size of the economy rather than increasing labor competition. And economic growth is a requirement for prosperity in capitalism.
Third, it may be possible for skilled workers in certain industries to maintain their wage premiums by organizing to restrict access to their special skills. However, this effort is almost invariably racist (and sexist, and anti-immigrant). The easiest way create an exclusive group is to base that exclusion on fault lines of identity and privilege already present in society. This can be seen in the whole racist history of skilled craft unions in the US. In addition to being racist, restricting access is, at best, a short-term strategy. As an industry matures over the long-run, employers will find ways to erode skilled wage premiums, whether by attracting a larger workforce, shifting production geographically, or changing technology to make the skills obsolete. The real goal for workers should be to improve wages and conditions for everyone. Of course, that's easier said than done.