1) You SHOULD disallow that. Why tolerate a system that creates incentives for that kind of abuse.
2) "dirty immigrant bastards" - You're assigning a point of view that the commenter isn't advocating at all. Protectionism is generally more about looking into the future and being scared for your ability to continue at your standard of living and less about disliking certain kinds of people.
And to add my own anecdote to this discussion without siding with anyone else's viewpoint (because I'm a special snowflake with my own nuanced opinions): I've worked at companies that chronically underpay H1B workers. The ones that got fair pay were the ones that were brave enough to demand it.