Don't worry mumofloads, you're not ranting 
I'm not actually that familiar with placing babies myself, excpept through her. My kids were all removed, all far too late. DD1 is terrified of her bios, shes been in therapy for years etc etc. I'm seeing a counsellor myself atm, because shes making more disclosures and I'm beyond being able to handle it on my own. So yep, i know exactly what you're talking about. They ddin't love my children enough to stop.
Our letterbox ddin't used to be vetted either, apart from one really good coordinator, who stopped a letter to DD1. It didn't have any cutesy phrases on it, instead it was addressed to DD1 and said that "don't you dare forget that you belong to me, you are my property" Went on to say that she was absolutely forbidden from loving me, and that if she didn't come and find them pronto when she turned 18, that they would punish her like she deserved. Lots of love your real and only mother.
They certainly aren't capable of doing anything loving or nice. Calling DD1's bio-f a sperm donor is insulting to sperm donors, most of whom are very lovely people who are trying to help others. DD1's bio-f does not fit my description of a sperm donor!
You definitely need to insist that your letters are vetted though mumofloads. It's really not acceptable that they aren't.
I don't really tend to use the term birth mother. Mainly because to me it suggests awoman who does nothing but give birth - and believe me, if she had done notyhing but give birth, then DD1 would have been a lot better off for it! And DD1 thinks in opposites - if she is the birth mother, then that makes me the death mother, because they are opposites, if that makes sense. Same with real mother, natural mother.
We use first parents, because that makes me the last parent - the last one she will ever have, the forever one. Or biological mother, so i'm the non-biological mother. Works for us anyway.
Yep, i have real trouble calling those people mother and father at all. i have an image in my head of a mother and father and they don't fit it! But DD1 will always be their daughter and tehy will alwys be able to call her their daughter, despite everything they've done, although i wish it wasn't that way 