Information can be valuable even if it originates from a person who has diametrically opposed views to ones own. Indeed had Marx not used the works of non-Marxists, Marxism would never have been born.
In recent years one of my favourite political commentators has been Nick Cohen, and in fact I am in the middle of his latest offering “Waiting For the Etonians” – who have now actually arrived. I don’t agree with Cohen on several points (his justification of the Iraq and Afghan wars, of course, or his carte blanch rejection of Historical Communism 1917-89). Nevertheless mentally arguing against him on these points is more intellectually stimulating than having what one already believes recited back in a text. On other matters – such as Cohen’s criticism of the cultural relativism that permeates the left today – I do agree with him.