He's being opportunistic because he's is using the dissatisfaction of the working class and their disenfranchisement from the political process (a direct result of austerity measures employed by the Tory government) to promote his particular brand of dog whistle politics.
My opinion of Farage is entirely down to his long history of barely disguised xenophobic comments, and bullshit stunts like this
'dog-whistle' politics is itself a dog-whistle, given how often the phrase is used whenever anyone dares question mass immigration