I hope they leave the graffiti there for all to see.
Reasons....
To show that racism against whites does indeed exist.
As a reminder that (as far as I know) the mainstream news media could care less, however if it were written about most any other group (except Jews, conservative minorities like black or Hispanic, etc.) they would be all over it. Even though the majority of times it turns out to be a hoax.
To proudly display the ignorance of those responsible.