D.X.
While what they did wasn't ideal, it really wasn't THAT bad. I don't think your son was put in any danger from drinking EBM that was reheated twice. EBM is way different than formula. Formula really does go "bad" quite quickly....like you're supposed to toss what's not eaten within 30 minutes or so (unsure of the time, since I exclusively BF my child).
With EBM, did you know that if you left a bottle of it out for 8 hours (that's no refridgeration!), it would actually have LESS bacteria in it 8 hours later than it did when it was first expresssed. Yes, it truly is a miracle food.
Hope that helps.