Not sure they are trolls - just completely uneducated / unexposed to what constitutes racism.
The obvious has been made illegal, but the "educated" racist will find another way. What you are reading is some posters struggling to catch up with the educated racist.
They'll get there.
I have to say the only time I've racist abuse in the modern era was towards a Ghanaian friend of mine from Brighton fans at an away game.
A few pissed up idiots.
On a positive note those games converted him to the Albion. I caught up with him recently after a few years and I'm dragging down to...