Likewise, people who responds to the Trolley problem by saying that they would call the police are not talking about the moral intuitions that the Trolley problem intends to explore. There's nothing wrong with you if those problems are not interesting to you. But fighting the hypothetical by challenging the premises of the scenario is exactly the same as saying, "I don't find this topic interesting for whatever reason, and wish to talk about something I am interested in."

In moral reasoning, that isn't necessarily the case.

Thought experiments in the ethics literature are used to determine one's intuitions about morality, and the subject there is not the intuitions, but morality, and the intuitions are merely a means to an end. But, ethics thought experiments are often completely unrealistic - exactly the places we'd expect our normal heuristics to break down, and thus places where our intuition is useless. So while in a sense denying the hypothetical is changing the subject, in this case it's more like changing the subject back to what it was supposed to be. ("You want to talk about my intuitions about this case, but they're irrelevant, so let's talk about something relevant")