Suppose a year ago I defended one position based with an argument. Then today I argue the opposite position, based on an entirely new argument.
Now someone says that my current argument must be false because I argued for the opposite position one year ago. Note that the person isn’t refuting my argument’s premises, logic, or conclusions; rather, that person is stating that my having argued against it in the past implies that my argument for it today must be false.
Is this a fallacy? If so, does it have a name?
Here’s an example, similar to the circumstances that have raised the question:
Lawyers for The Developer argue that a land use law implied X in a court proceeding. A year later they argue that a land use law implies Not-X based on an entirely new line of reasoning. Ignoring whether the new argument successfully beats the old argument, the attorney for those opposing The Developer assert that The Developer’s argument for Not-X doesn’t pass muster because one year ago, The Developer’s lawyers argued in favor of X.
The attorney for the opposition does not address The Developer’s new argument in any way, shape, or form, but merely states that because The Developer went on record for X in the past, then his argument for Not-X today must be bunk.