It's hard to explain a taoists perspective on duality. It's not bullshit. A lot of it is simple and complex at the same time.
Take the 2nd chapter of the Lao Tzu's writings which inspired the quote:
LETTING GO OF COMPARISONS We cannot know the Tao itself,
nor see its qualities direct,
but only see by differentiation,
that which it manifests.
Thus, that which is seen as beautiful
is beautiful compared with that
which is seen as lacking beauty;
an action considered skilled
is so considered in comparison
with another, which seems unskilled.
That which a person knows he has
is known to him by that which he does not have,
and that which he considers difficult
seems so because of that which he can do with ease.
One thing seems long by comparison with that
which is, comparatively, short.
One thing is high because another thing is low;
only when sound ceases is quietness known,
and that which leads
is seen to lead only by being followed.
In comparison, the sage,
in harmony with the Tao,
needs no comparisons,
and when he makes them, knows
that comparisons are judgements,
and just as relative to he who makes them,
and to the situation,
as they are to that on which
the judgement has been made.
Through his experience,
the sage becomes aware that all things change,
and that he who seems to lead,
might also, in another situation, follow.
So he does nothing; he neither leads nor follows.
This is not the best translation, but does give a good example of the theme of duality.
Can you look at something without naming it?
Buddha said 'the best weapon is your enemy's mind'. What would be a better way to get at your enemies mind other than splitting it in two?
Do you see now what I am getting at? Now the concept of duality is your minds worst enemy.