My father used to describe my mother's characteristically circular argumentation as "illogical". It is however a debating technique with a pedigree that dates back to the finest logicians of the middle ages. Thomas Aquinas for example, counselled his students that "when you meet a contradiction make a distinction".
In common parlance this is known as moving the goalposts. The more sophisticated practitioners don't just move them they simultaneously re-construct them, or more subtly, re-describe them. My mother on the other hand limits herself to turning up the dial on the emotional content of the discussion at hand - this has the effect of sharpening the background mood for all participants, making the exchange of neutral rationalisations an increasingly unlikely outcome.
I might have come to regret having a parent like this but for the fact that I increasingly have to deal with similarly-disposed logicians in my professional life. Instead I find that my childhood experiences have left me remarkably well-equipped to anticipate the direction that life's goal-mouths intend to shuffle off in, a skill that nevertheless leaves me prone to bouts of frustration and more occasionally, a debilitating sense of futility.