Earlier quoted context omitted.
Sorry, but I don’t see where it says he has to respond to a woman’s nonsense flirtatious mysticism by lowering his own standard for discourse down to her level. He does not have to tolerate her magical thinking. I think he drew an interesting correlation between racism and her astrological beliefs that she likely has never heard before, and perhaps will give her some much needed introspection. That is a far more mean…
I agree with you, I think "just be yourself" or else get comfortable acting on the other hand, it's also important to 'go with the flow' sometimes, specially around things you don't consider too important; whichever those may be (I've noticed that what is important is even affected by my mood).
In any case, it depends on what you value. If you don't care that someone is into astrology, then go with the flow. If you deeply believe in science and it's one of your core values that people close to you believe in that as well then a short and polite conversation is all I see happening. I'm of the latter kind. I'd have never made such a strong comment though as it is my experience that people aren't really open to change their minds on this (having done readings on a few dozen people as a kid). So why waste the time?