There are situations where GP is correct, because there is an alternative to the H1B. Employers can outsource the entire department.

Outsourcing has risks, though. These risks are especially difficult to mitigate in "real" high tech where IP and trade secrets have real value. Outsourcing risks are also difficult to manage in cases where sensitive customer (or valuable company) data is being handled. In these cases, companies will only outsource when they really cannot find domestic labor, full stop. (Remember that >60% of CS PhDs go to immigrants.)

In these cases, H1Bs allow the job function to stay completely onshore. So then local employees benefit from the fact that they are easier to hire when companies over-shoot layoffs or lose H1Bs due to ratios.