Perhaps you did not understand.
I read marktwain's comment as containing listing of leftist inner thought --- not endorsement of those thoughts.
In fact, the listing was demonstration of what is wrong with those people's presuppositions, and the fruit of that among godless (but ever-so virtue signalling) "progressives".
Like Ronnie (Raygun) said decades ago;
It has gotten worse. The progressives have been progressing along the well predicted paths, well predicted even from back in Reagan's day.
Now they turn towards both rhetoric and action of Rage and Violence -- justified by exalting their own self-perceived virtue while demonizing/dehumanizing any and all who disagree with themselves, painting their opposition (that would be people like us here at FR) as Nazis, racists, whatever...
Being nationalistic does not necessarily equate with being fascist. American U.S. constitutionalists cannot be "fascist" without going against the Constitution. We are being daily accused. But the leftists are wrong. A nation, and THIS nation in particular CAN legitimately and Constitutionally control access to it's own lands, barring anyone from entry for any reason.
Not every person born on this planet is born with U.S. Citizenship "rights". Those [citizenship] rights are being blurred with basic human rights -- the latter coming from God, not from any government. To put this another way; Not everyone born on this planet is born with God-given right to immigrate to the United States. We, The People who are already here do have a say in that through our elected representatives -- according to the Constitution-- and laws already on the books (Codes of Law) which the Legislative Branch of the United States is empowered by the Constitution to write. Immigration codes are among those which are in fact Constitutional.
The US, in a centrist view, is willing to take on anyone new who in turn is willing to be a team player here. This is even seen in the willingness to consider lenient treatment of those who were brought in as minors against their will under the extralegal DACA but have somehow managed to integrate (which might be a minority of them, but it isn’t zero).
We are being told to swallow an invasion of non team players.