Can someone explain this?

Amnesty advocates assert that providing legal status to illegal aliens would reduce the cost of "undocumented immigrants." That is akin to arguing that the way to reduce speeding on the highways is to abolish speed limits. Doing so would eliminate speeding, but it would not eliminate the danger of operating vehicles at excessive speed, and, arguably, would have the opposite effect. Similarly, converting illegal aliens into legal residents would reduce the size of the illegal alien population, but it would not reduce the overall fiscal outlays associated with that population, and arguably would significantly increase them as the newly legalized residents became eligible for public assistance that was denied to them while they did not have legal status. It would also lead to additional illegal immigration as happened following the 1986 amnesty, which would further increase the fiscal burden.

Wouldn't the newly realized income tax be in excess of additional capital outlays to newly legalized immigrants? It even says here:

Yet, it should be kept in mind that the $3.5 billion in tax collections is not truly an offset to the fiscal costs, because similar, and likely greater, tax revenue would be collected if the same jobs were filled by legal workers.

So, this statement supports that making illegals -> legals would increase tax revenue. The previous quote says illegals -> legals would increase tax expenditure. But there doesn't seem to be a clear comparison of the two figures.

Now, Cali is proposing a budget that puts it at a miniscule $2B deficit ( http://www.ebudget.ca.gov/2016-17/pdf/BudgetSummary/SummaryCharts.pdf ) -- this makes me assume that the average citizen is a net positive on tax flows. That is, for each additional citizen there is more tax coming in rather than out. I say this because although there's a deficit, I assume a large part of that is for fixed expenditures (infrastructure mainly).

So from the purely economic perspective this piece takes, doesn't it make sense to provide amnesty to these people?

I'm Canadian, so please bear with me if I'm unfamiliar with certain realities.