life isnt fair you know but i do understand where these companes are coming from.. no one wants to get sued you know.. if one little mistake occurs and a client or customer gets infected.. there goes the company and its capital
these companies try to protect themselves from something that may never ever happen but chances are not zero still
i wish your son the best..maybe one day hepB becomes something of the past for all
Personally, I don't like the law forcing down decisions on private citizens' throats. Even if the private citizen happens to be an employer. I will fight for the right to make my own (possibly stupid) decisions as long as I am not trampling someone else's rights.
I would try to convince other people that I am no danger to them only if it is worth my effort to do so. I have no idea; can you tell me how easy or difficult for your son to find some other equally satisfactory assignment? I ask because given the choice, I would discriminate in favour of a more sensible (according to my own views and perceptions) employer.
Unfortuately situations like this is not uncommon.
Employment laws vary amonst countries and I don't know anyone here could guide you in any legal matter.