1. Imply that Quantitative Data is Inherently Flawed:
If you don't feel that accusations of an inevitable and pervasive bias are a strong enough slur against the principle of empirical data collection, be sure to make bold assertions to the effect that the whole principle of obtaining quantitative data on people is an act of "violence" on the holistic truth about humanity.
2. Remember that a Focus on Subjective Experience is the Only Worthwhile source of Knowledge:
3. Remind People that You Aren't Interested in the Entity Being Studied:
4. Accuse Anyone Deploying Empirical Reasoning Of "Scientism":
This one is particularly effective because very few people actually know what it means. Sciencey people all hate religion don't they; so if you accuse them of an irrational faith in the power of science you can win any debate while simultaneously getting on their nerves. Ignore the fact that a belief in the use of the best available empirical evidence is not even close to being scientism proper, anyone who dabbles in science is unlikely to have retained their common sense and will almost certainly be out of touch with reality. If someone has used "Schizophrenia" or "Bipolar Disorder" in their work then they plainly believe these entities to be illnesses just like Hepatitis or diabetes and certainly don't have any curiosity regarding their ontological status. They are no better than mystics or astrologers, and anything they say can be dismissed.
5. Remind People of the Nazis:
Scientists always drift back towards biology and genetics, they can't help themselves. Even if they are only suggesting that genetics and constitutional physiology account for a relatively small proportion of variance in any given problem, there is no telling how long it will take before they drift towards a policy of eugenics and ethnic cleansing. You are only ever doing anyone a favour by reminding them of phrenology, eugenics and--ideally--the Nazis before they walk foolishly out onto this slippery slope.