Is the following tactic a sort of known debating/argumentation fallacy, and does it have a name?
Bob and Rob debate a topic. Bob provides a number of points to support his position. Some are strong. Other are more arguable and can well be attempted to be rebutted.
The latter is what Rob does. He simply ignores the strong points as if they were not made, and focuses on comprehensively showing how weak the other points are — presenting the conclusion that the overall Bob's reasoning has no merit.
This sounds similar to the argument from fallacy. The argument from fallacy is when a person says that if a particular argument for X is fallacious, then X must be false. Rob is doing something like that. Rob says that a particular argument of Bob's is wrong, so Bob's conclusion must be wrong, regardless of the other arguments from Bob.
However, it is also possible that even the points Bob thinks are strong can be rebutted, and that Rob is laying the groundwork to do just that. Perhaps if some of Bob's assumptions, as shown in his other points, can be refuted, then Bob's stronger arguments also collapse or weaken.
It might be said that Rob is being Hermeneutically uncharitable. That is, Rob is trying to defeat Bob, rather than engage in useful discussion.
Daniel Dennett might say Rob is engaging in the tendency to caricature one’s opponent, the antidote of which is to "steel man" any argument before attempting to make a case against it.
