I agree with others, it was his decision. It was his right to make his feelings known on the issue, for whatever reason he has - be it grief, personal hangups, or even vitriol for his ex wife (though I honestly doubt that actually is a major part of it, not saying it isn't any of it, but I doubt it is much of a part). Agree with it or not. And it is none of our business why he made the decision he did.
All that said, I think I can understand not wanting to allow his daughter to be used after death in such a way. Both in terms of grief -that would be a HARD decision for me- and, maybe, in terms of personal feelings.
My father is against organ donation and transplant on a personal ethic. He finds it a miraculous medical feat, he respects the doctors that do such amazing things, he understands people feel differently and respects that. But he personally feels it is unnatural and "wrong" on some levels, to have a part of another person inside and part of you in such a way. I understand that.
I personally feel much the same, honestly. And I have stated to my family before that were it to come to the point of me needing a transplant (which, with my medical issues, is a possibility in the future) that I would refuse. Both because I feel the same as my father AND because I feel those same organs could be, potentially, put to better use than on me.
BUT I am also a listed organ donor, and all my family and loved ones know how I feel on the issue - that I AM to be offered as an organ donor, whatever organs can be used at my death (which, admittedly, may not be that much, since I have bad eyes, weak bones, bad lungs, damaged pancreas, and possibly a damaged liver and kidneys from years of medical problems and meds). That it is my wish and they have agreed, despite my fathers objections to the issue personally, to see that carried out.
(My mother is also listed as an organ donor, so my family knows to do so for her as well.) I would rather my organs be used to save a life in my death despite personally having objections to being on the receiving end of that same.