"Valhalla, what do you mean by 'all manner of rejection of the breed'?
If I see a Staffie I avoid them. They are scary looking things and you can't deny the media portrays them as lethal when they attack.
Fair or not, who would risk a dog like that running around one's child?"
I mean rejection by irresponsible owners and by potential dog adopters based on sensationalist reporting in the media, inaccurate information, anecdotal "evidence", scare stories and all these being backed up by those who perpetrate the myth that all SBTs as dangerous and to be avoided based on these factors and similar ones.
SBT's are NOT "scary looking things". They may be so in your opinion but that alone does not make them scary looking things. And yes, you have made precisely the point which I am trying to, the media DOES portray SBTs as lethal, which is as intelligent as portraying men as lethal following a murder by one human male.
"Who would risk a dog like that running around one's child?"
WHAT???
A dog like what? A dog that is in YOUR opinion "scary looking"? 
A dog which has done nothing wrong but whose entire breed you're discriminating against?
F(Dogs)S please judge on a dog by dog, case by case basis and blame the deed, not the breed.
Nesta, as the owner of 2 GSDs and another large breed myself, if someone came to visit me and chose to stay in their car until I put my dogs out of their way (unless they were genuinely phobic like the OP or allergic), they had best bring their sleeping bag because they'd have a bloody long wait.
Until Hell freezes over comes to mind... !
LaLoony, are the other issues/concerns you have with your PIL able to be addressed and is the dog problem the main one? I just get the impression that yours isn't an entirely comfortable relationship overall.
Good on you for not transferring your fears to your son. I'm petrified of blood tests and needles and have been less good at hiding it.