Alternately, they say: "Uh, actually, I was enjoying that conversation. In particular, I was interested in the part where [stuff]. Maybe we could focus on talking about that part?" And then maybe you compromise on a conversational topic, rather than interpreting the rejection of the conversation as a rejection of you.

Or in the ideal case, "Oh, I wasn't actually enjoying it either, I was just talking about it because I thought you still wanted to. Great, let's change the subject."