Friedman argues that the H visa amounts to a subsidy, more or less, for businesses. He makes a fairly convincing argument, although I disagree with many of his conclusions.
This stuff crosses party lines. Historically, the Left always objected to immigration, although in the last 20 years or so the Right has come to the point of being more vocal about it. I'm not sure why, exactly.
Tell us more about the left opposing immigration... It doesn't jibe with the bits of knowledge I have about it, which are that Ted Kennedy is the father of our modern immigration policy, and that opposition to letting in more Jewish refugees in the 1930s came from Republicans and conservative Southern Dems in Congress.