I really think it's about community standards. In the community where Randya and I live, our community generally supports ghost bikes, or at least tolerates them. Our city government seems to tolerate them so long as the memorial is periodically maintained. I am sure in other communities, that is not the case.
I've also never though of ghost bikes as being accusatory so much as a memorial and recognition that a human being died in that place where the bike is located. Perhaps that is another example of different community standards, or maybe it's just a reflection of the cyclists I know and socialize with.