I'm actually pretty shocked reading the general consensus on this thread TBH. Why on earth would anyone suggest going NC over this issue?! Why would you put money before family?
When you are disinherited, of course it's about the money. What else would it be about? At least your DF has told you of his intentions before his death. It often isn't that black and white!
My DM was horrified when her DF disinherited my brother and I, leaving everything to my cousins. I wasn't. Their logic was that my brother and I were far more intelligent and thus had a far greater earning potential. I actually admired their thought process as its true - they were leaving their money to those who needed it more. My cousins earn virtually minimum wage and none of them can afford to buy a property - yet my brother and I own our own houses (I have two) so actually, their thought process was spot on. It didn't show that they didn't care. It showed that they wanted their money to go to the people who needed it.
In my current situation, my house goes to my DH and vice versa - not to the children. The reason being that this will put us both in a better situation to care for the family. My DIS benefit goes to my DD because I know my step sons will inherit from their grandparents, and my DD won't. Does that make me an evil stepmother? I don't think so, because I know my step sons are accounted for elsewhere.
My DF remarried ten years ago (he's married to someone my age). He has a will; I have no interest in seeing the contents. If he leaves it to my SM then so be it - they have a LTR so that's HIS choice. I wouldn't be so selfish as to cause frictions over money. Ultimately your finances are your own responsibility and it would be crazy to rely on a theoretical inheritance!
And FYI, when the person does die, you won't want the fucking money anyway. It's tainted. My DM died very suddenly, aged 62, and intestate at Christmas (leaving me, 30, and my DB, 27) and it was the worst thing ever that I didn't know what her wishes were. I'd rather she had a will, even if I wasn't in it. So I'm in the position of having to guess what her wishes were and hoping I get it right.
Without knowing the exact financial circumstances of everyone involved, and how the estate is composed, it's impossible to judge the OPs DF as doing the wrong thing!