What you are describing is called a snuck premise.
An adversary will ask a question or make a statement in which some premise is assumed to be true or taken as a given, and that premise is typically eludedalluded to in some way, such as asking a question about its consequences. In this way the adversary is trying to sneak the premise into the question or statement as an unstated assumption.
By answering the question or debating about the details of the scenario given, it can be construed that you have accepted the premise, even though you may not necessarily agree if it was stated explicitly.