1) So basically your explanation goes like that: "Discrimination against immigrants is justified, because it's a law and other countries discriminate even worse than the US".

I hoped for somewhat better reasoning than that. If you take "it's a law and it must stay unchanged" principle to the heart, then you would be dead by now killed as invader by one of American-Indian tribes.

2) "Opening borders to everyone" has very little to do with "Stopping discrimination against immigrants".