Judge Matthew Kacsmaryk, a federal judge in the Northern District of Texas, ruled on the EEOC's treatment of Title VII employment discrimination claims on gay and trans people.
If sexual orientation, gender identity aren't a protected class, then you can legally not hire people for their sexual orientation and gender identity. E.g. you could completely, legally, not hire straight people and it would not be illegal discrimination because those categories are not considered illegal to discriminate against. It's legal to discriminate on many things in hiring; you can discriminate against stupid people, people who show up late and unprepared, people who don't have a degree (relevant or not for the most part), etc.
The point of Op you're responding to, is that it would be completely legal to approach hiring like that in this legal dystopia.
So you can't be fired for being a member of a protected class, but discriminatory dress codes and bathroom ruled are OK? So they can have these rules, but can't fire you for violating them, because you are a member of that class?
SCOTUS ruled in Bostock v Clayton (2020) that that 1964 Civil rights Act protects employees against discrimination on the basis of sexual orientation and gender identity.
I guess they are teeing this up to see if the current SCOTUS will overturn their previous ruling.