I just read the thread and I thought I would throw in my two cents.
I went through something very similar with my ex-boyfriend, where he would get very defensive every time I would try to express my feelings about him getting tested. I think personally most of it is fear, and them not wanting to know the results. The other part of it could just be pure ignorance, some people dont think THEY will EVER contract something. You know, the whole "it wont happen to me" syndrome. Either way, if its something you feel very strongly about (trust me, I dont blame you), then I would sit him down, and say exactly how you feel and tell him basically that if he cares for you then he will try atleast TRY to listen, and understand where you are coming from.
If he still doesn't want to hear it, maybe rethink things with him?