I'll bite.
Data can do a lot to improve discussions about history, politics and business.
I'd also argue that data can improve discussions about seemingly subjective things such as design.
> And NO, sorry, pure facts many not be enough or might be incomplete or out-of-reach for that subject-matter.
In fact I'd say that I'm close to saying those are the only discussions worth having about certain topics.
If I like a design and you don't that brings us nowhere. If either of us can bring some data and say 72% of the testers prefered it strongly, - but colorblind people struggled with it - that is something that might give both of us some value and might lead to better results.