LONDON, Nov 18 (Reuters) – If Saudi Oil Minister Ali al Naimi wants to stop conspiracy theories spreading before a crucial OPEC meeting next week, it’s too late. Naimi’s intervention last week after a two-month silence failed to address a question energy markets want answered: is the OPEC leader no longer willing to defend oil prices which have dived by a third to their lowest since 2010, and is it pursuing new commercial or even geopolitical goals? […]