Reformists and some centrists (the British SWP for example or the American "Trotskyists") avoid the use of dialectical materialism and their method of thinking is a form of western Pragmatism and formal logic. Other centrists, like Alan Woods of the IMT and Peter Taaffe of the CWI explain the dialectics method in general, but they are unable to apply it to revolutionary politics.
For example in the war of imperialist Britain and the semi-colony of Argentina in 1982 they did not take the side of Argentina. The same in the war between the US imperialism and the Afghan people led by the reactionary Taliban. They have refused to stand with the Syrian revolution because it has been led by Islamists. When Fatah backed by Israel attacked Hamas, Alan Woods refused to defend Hamas and stated that in a war between two factions in Palestine, the IMT does not choose sides.
To conclude, Marxists must take into account the consequences of the victory of each side in a war, the potential gains of the imperialists or the struggle of the working class and the oppressed masses against it, the advancement or destruction of the forces of production of the colonies and semi-colonies, the strengthening or weakening of the control of the imperialists and the super exploitation of the working class, etc. For revolutionary politics it is necessary to use materialist dialectics which is the philosophical basis of our scientific observation, thought and action.