It is now all my fault

I've just received a nasty e-mail from my son. He says the social worker is a demon I let in and he will never,ever get access to his daughter. This is all clearly my fault and he does not want me to call him anymore.
I feel strangely calm about all this. At least I now know where I stand.
He is given to making dramas so I don't believe any of it.
What does bother me though, is he has accused me of telling lies. I have always tried to be completely honest about everything. Am I being over sensitive here? He lies constantly so is not in a position to accuse me.
This has only ever been about the welfare of my grandchild and if he has turned his rage against me instead of his partner then so be it.
Isn't parenthood just wonderful?