> You can start to explain that if the researchers both flat out state their approaches and assumptions in interacting with their female subjects.

I would think that the foundation behind your argument - which I agree with - implies that this isn't actually possible. You have an infinite regress of biases.

Empirically, what you can do - to take your example of those menstruation researchers - is to get more data from researchers of different backgrounds to try and statistically isolate those biases. This is part of "standard empiricism". You also always have to live with the fact that data is sometimes too noisy to be meaningful.