A polemic for revolutionaries is a militant dialogic practice to reveal the contradictions of a position, hammering it down to break open its hardened crust in order to rescue life from the stifle of the canon.
In Marx and Engels’ Collected Works volume 47, I found a very interesting letter written by Engels to August Bebel. It was written about a month and half after Marx’s death, April 30 1883. Bebel seems to have suggested Engels to move somewhere else in Europe. Engels’ justifications to continue staying in England is quite remarkable.