Lump of labour nonsense -- a claim I certainly didn't make -- is your response to VCs/large employers doing their best to leverage h1bs to reduce wages for software engineers? If that's the best you can do, let's just call that you conceding the point.
You didn't make much of any point; you simply claimed there was a 'giant externality', without saying what it is.
The thing most people complain about are how software developers will be reduced to penury if people from other countries are allowed in the US. Were you referring to something else?