You make a pretty good point.
The mind originates from the brain, experimentation strongly suggests.
In my mind, overcoming that bias is the definition of rationalism (ie, empirical truths are not fundamental truths).
If you're not going to trust empirical evidence, what on Earth are you going to trust? How is dismissing empirical evidence the definition of rationalism?
I did a search about property dualism and I couldn't see much written here on this site.