Possibly my intention with that comment was unclear because I quoted too selectively in my zeal not to clutter things up; my apologies.
Why not? A common man or worker can be just as racist as socialists. There is no reason that common "average Joes" are somehow immune to the idea of racism or desiring war.
Why are 'worker' and 'socialist' mutually exclusive categories? Why are socialists assumed to be racist? I guess it's a typo for nationalist?
Anyway, sure he can be, but:
a) He generally cares more about food on the table. So, in the end, does everyone, but he faces the prospect of food not being on the table, so...
b) Following from that, working class prejudice is generally against people supposedly keeping the bread off the table rather than supposedly menacing the international position of the nation. Where I come from, the victims of working-class racism were the Catholic Irish and the Italians, not the Germans about whom the jingo press were in a fankle. It took some time for anti-German prejudice to catch during the war, it didn't last, and it got some of its life from anti-semitic undertones.
Similarly, the Bohemian-German working classes among whom the early forms of Nazism arose were notoriously anti-Czech because the Czechs were competition. But Hansi from Hamburg? I can imagine that he doesn't like Poles much - although the Poles in the Ruhr seem if anything to have assimilated faster than the Irish in the west of Scotland, thanks no doubt to the religion issue - and that he thinks Russia is a strange, threatening, barbaric country, as the majority of western Europeans do.
That doesn't translate into membership of the Pan-German League or any other urgent concern for foreign policy matters, which brings me to...
c) The workers, in a time of strikes, socialist parliamentary ascent, and middle-class anxiety, have obvious reasons to be opposed to some of the key constituencies of chauvinistic nationalism and imperialism at home.
And I do recall hearing somewhere that the German masses, having been told that the war was in self-defence by the the SDP and others, were shocked to see their country occupy Ukraine, though I can't remember where and wouldn't vouch for it.
Anti-slavic(and even more anti-Polish) feelings were pretty widespread in German society, especially in old Prussian territories where this was somewhat part of cultural tradition.
The question here is not whether the working classes in the different countries could be convinced to fight each-other: we know that they were. It's whether they were going to demand a fight in the absence of any other reason for one, for which I see no evidence at all.