I think the aunt was rude for pushing to watch the channel after she had been told no. The OP says they had settled down after dinner specifically to watch TV; but when the aunt kept pushing for the channel the OP didn't like, the OP offered her alternatives, such as watching a DVD or turning the TV off to play cards. The only other suggestion I might have offered was that aunt could watch her channel for a set amount of time while I went off to do something else--like, "Well, I'll go read in my room for an hour and you can watch TV. Then maybe we could play cards." I'm the sort of person who would actually love that, because I would want to have some time on my own instead of being constantly in the other person's presence. But, it also depends on the logistics of the situation--if there's nowhere the host can go where they won't hear the TV, for example, or if they have no other appropriate activity they could do for an hour.
I think ultimately, a host can control what activity happens in their own home, but a guest can control whether they participate or not. So a host can come down and say, "The TV WILL be turned to this channel/TV show now!" but a guest can say, "Okay, I will go to my room for a while then." I think it would be rude for the host to respond, "No, you MUST sit and watch this with us." If the TV is in the guest's "room" (like they're sleeping on the living room couch) I think the host needs to either NOT insist on that particular use of the TV, or they need to provide the guest with an alternative place to go (like maybe the host's bedroom). The tone of this interaction can also vary greatly: it could be tense and uncomfortable, and be the last visit ever between these two people; or I could also imagine it being handled very graciously. "Oh, I like to watch my show at 9, but I know it's not for everyone, so can I make you comfortable in the other room with some tea and a good light for reading?"