An Imaam in a Musjid here in Gambia, vigorously prevents musallis from leaving their hands at their sides during Salaat as is the practice of Maalikis

Answer

This imaam must be some Salafi moron. Both Irsaal (leaving the hands at the sides) and Wadha' (folding the hands) are valid practices in the Maaliki Math-hab. The more preferred view of the Maaliki Math -hab is Irsaal in the Fardh Salaat, and Wadha' in Nafl Salaat although both are permissible in Fardh Salaat. There is no need for a dispute on this issue. But these Salafis are incorrigibly stupid.