It's discouraging when you see people taking years to cotton on. I try and frame it, in my mind as "well, at least they finally do see it", and also. When people reach these conclusions themselves, of their own volition and experiences, you know that change in seeing things is for keeps.
It's frustrating but at least there's no going back, and a person who comes to these realisations freely, is a true ally whose experiences and change in thinking have come about because of hard, long soul searching. You can't buy that, nor push a person into it.