you meant to be insulting
No. Not at all, but feel free to think that - you certainly have plenty of varied views.
it would seem to me that they should know what they are talking about
We all do. As I said, this is a political issue first and foremost.
You still haven't mentioned your time in PL or exposure to the culture of PL. If I comment on things in the US, I can say at least that I've been there a few times and frankly any English speaking person gets some exposure to their culture.
Not even one who learned very little about Polish grammar because he spent most of his school-days carving swastikas (backwards ones most probably) into desks? Magda appears to be too naive to even know why a racist might want a black person to be near a tree. But if you prefer to say that the graffiti must have been written by a foreigner because all Poles have perfect knowledge of Polish grammar, go ahead.
Absolutely. Hit. Nail. Head.