can't speak for "him", but perhaps he means that the overwhelming majority of workers in america; 1) do not belong to unions, and 2) have a less than positive view of unions and do not identify with them, or they might belong to them...
the reasons for this are numerous, but hardly because workers "dislike themselves", but more because they don't see "themselves" as represented by unions, any more than they see "themselves" as represented by the ruling corporate parties...
this is not to say that being in a union isn't better than not being in a union, only that under present conditions, that tends to be a lesser evil - like choosing between those parties - and not a real solution to major political economic problems.
fs