In general, we find that Marx and Engels both use the word barbarism in the way that was typical of their day, in the contrast historical and geographical between the civilised and barbarian world. Occasionally, they describe features of the capitalist world as barbaric (though never the society as a whole, because that would make a nonsense of their conceptual framework). The force of that condemnation, of course, is that the danger is that capitalism would revert to barbarism, i.e. step backwards into conditions so barbaric that they would be comparable with the preceding period when barbarism was the norm.
The trading nations of ancient times existed like the gods of Epicurus in the intermediate worlds of the universe, or rather like the Jews in the pores of Polish society. The trade of the first independent flourishing merchant towns and trading nations rested as a pure carrying trade upon the barbarism of the producing nations, between whom they acted the middleman. Capital, Vol III 438
'the class that represents barbarism within civilisation', i.e the peasantry Class Struggles in France, 79
'Society suddenly finds itself put back into a state of momentary barbarism' Communist Manifesto, describing economic crisis, as a descent backwards into the past, p 16
Objecting to the way that 'The Middle Ages were regarded as a mere interruption of history by a thousand years of universal barbarism.' In the German Ideology, Engels insists on 'The great progress made in the Middle Ages-the extension of the domain of European civilization.' 26
'The antagonism between town and country begins with the transition from barbarism to civilisation, from tribe to State, from locality to nation, and runs through the whole history of civilization to the present day'. The German Ideology p 98
In The Origins of the Family, Private Property and the State, Marx endorses Lewis Morgan's schema of 'the three main epochs, savagery, barbarism and civilisation', 24, and see throughout.
Engels writes that 'Fourier is at his greatest in his conception of the history of society. He divides its whole course, thus far, into four stages of evolution-savagery, barbarism, the patriarchate, civilisation. This last is identical with the so-called civil, or bourgeois, society of to-day-i.e. with the social order that came in with the sixteenth century.' Socialism, Utopian and Scientific, 49