I was never into debating societies and such (despite someone on GN a few years ago saying that all posters should be able to logically defend their point of view, with evidence, because "everyone did debating at school".
However, it does seem that one feature of debating societies is that people are told "Next week we will be debating (insert the subject) You, X, will be speaking for this, and you, Y, will second it. You, A, will speak against it, and you, B, will second that." No need to have a genuine opinion, it is an exercise in being persuasive for the sake of it. Good training for a political career.
The result of some people in some schools having "debating experience" of this kind is that they become practiced at arguing strongly and persuasively for or against something without necessarily having the slightest interest in it, They are adept at using tactics that could put their "opponent" off their stride - like throwing doubt on their credentials or integrity, sounding scornful of the quality of the evidence they have produced and acting amused at their naivety.