Earlier quoted context omitted.
I don't see how laws can prevent discrimination, to be honest. LLs can refuse to rent to anyone for arbitrary reasons without being required to divulge the true reason.
It being illegal means you can drag the landlord to court and ask them to explain their thinking to the court. You can say, look, here's the income and rental histories and credit scores for your tenants in separate apartments, here's documentation saying we are above that, so what's the reason for the rejection. And, lying under oath is its own crime. This is like saying "murder shouldn't be illegal because everyone…
And how do you prove that? A lie isn't the same as a body.