Possibly the guy was a bit of a dick and Dilbert of course redirects his rage to his skin colour and ethnic origin because Dilbert thoroughly conditioned himself to see that as the foremost and only factor influencing others' behaviour. Most all he tends to couple negative traits: pakistanis and indians are swindlers/dirty, africans are violent & dumb, asians are two-faced and plotting, but their women are kinda cute and submissive I guess so the manly westerner Dilbert wants to fuck them.
I wonder how he perceives his own British roots and his place in AUS society. Heaven forbid others would associate him with chavs and other working class dregs from London. Or perhaps he's by nature an elitist, conniving and manipulative person, growing up the son of daddy the diplomat. Are all aus people the sons and daughters of criminals ergo pieces of shit? Or are these surface judgments unfair?