You reflect what you see at the present. This has not always been the case. One was proud, for instance, to work for defense in 1950s-1960s and stand up against the Russkis --- particularly after Sputnik. And people who did that were treated with respect.
One is more likely to join the army having heard respectful stories from parents about fallen heroes. One is much less likely to do that seeing Vietnam vets spat upon when they return home.
One is more likely to want to become a professor --- a class in itself in largely classless America --- when professors are learned intellectuals. And, conversely, one is less likely to do so when they have become working bees that know nothing outside of their narrow field and churn out uninspired papers.
All of the above have been observed in this country until very recently. I consequently think that you are shortchanging a bit American culture in general. It is very true that, today, what you said is correct: the culture is very materialistic and even base. The problem is therefore not the visas but the state of the culture.
I don't think I quire confirmed your position in the previous post. If your parents beat you up, it does not help if one exiles your neighbors who do not. To be sure, you will not know that your situation is abnormal, but it will not become better. Similarly, if our students are ignorant and unwilling to work hard, it will not help to prevent good students and faculty from other countries from coming here. All we will achieve is ignorance: we will not know how bad we will have become.
Finally, I never said that completing a degree in law is easy. But is is an incontrovertible fact that a mathematician visiting a seminar at Harvard Law will understand the topic and the points made bt the speaker; he will be able to read a juridical paper; but the converse is false: even with an undergraduate degree in mathematics a jurist will not understand even a word at a mathematics seminar. It is incontrovertible that intellectual barriers to entry are much higher in mathematics and theoretical physics than in, say chemistry; and in chemistry higher than in law. There are no barriers to entry for understanding anything at all one may hear at a seminar on Dickens. I am not splitting hairs: this is relevant to why "hard" disciplines suffer first in a culture that has dumbed down education.