I'm sorry, I have broken the cardinal rule, and haven't read the full thread.
For me, I'd be asking my daughter, what does she think she will do with regards to her father's views on inclusion in buying him such a t-shirt, for his birthday no less? Is this likely to make him receptive to her message and beliefs, or is it likely to entrench him in his own, still further? If the latter, is that then a particularly responsible thing for her to do, in line with promoting her views? If this cause is truly important to her, then surely she wouldn't want to do something that is likely to make it even less likely that somebody would be less hostile, or more open and receptive to its messages?
My father was a bigoted dinosaur until the day he died. I loved him dearly. He was a very intelligent man, but very old fashioned and rigid in his views, and there was a point at which I absolutely refused to discuss or debate certain topics with him, because I disagreed with his views strongly, and refused to continue to be browbeaten from his position of authority into even implicitly acquiescing with them. That would have been around 15, 16.
He had his right to his opinion, and to express his opinion, and not to listen to my opinions. I had exactly the same damned rights. Once we both agreed to exercise our rights, in particular, right c, we got along a heck of a lot better - and it was a lot more peaceful for everyone else in the household!