RE: All facts are subjective

Consider anything that you or we recognize as a physical object. We presume that there is something there that has objective existence and that constrains our perception of it. But we have no way of knowing the objective reality, or even knowing for certain that there is any physical reality there. If we were in some kind of sensory ‘fun house’ or hooked into a computer that simulated reality for us (ala The Matrix) we would still have the impression of a physical reality, just as we sometimes have when we are dreaming. But then we awake to discover it was all ‘illusion’. We have only our subjective, cognitive model(s) of the physical reality. And all facts, all knowledge, is subjective, at best a perception of a presumed objective reality, not the objective reality itself. 
Moreover, the models we do have make it pretty clear that whatever the objective reality may be, it certainly isn’t what our models are. There is no ‘chair’ or ‘leather’, except in our minds. Those concepts are parts of our model, not elements of an objective reality.