Cynicism is definitely a virtue in a certain light. Trust is good for everyone while being bad for the individual, cynicism is good for the individual while hurting society.

Personally I think both extremes are terrible, but leaning on the side of cynicism seems safer.

Of course there is: soft => more refined and subtle, cynical => more wise to the world.

I read "soft" as more mellow and chilled out, and less stressed about (what seems) trivial stuff. In a way, even kinder. And from what I've read by rich people (such as Diane Disney Miller) cynical is a lot about the difficulty of establishing genuine relationships.

That is how I read it as well. I’d imagine being someone that is cynical and wealthy protects your wealth from forces that would suck less cynical people dry (multilevel marketing, get-rich-from-real-estate seminars, stocks currently riding the wave of the hot rumour of the week).

An important detail is that the quote is not "they are soft and cynical", but rather:

"soft where we are hard, and cynical where we are trustful"

In other words, how they are different from others. Not that they are fundamentally soft, cynicalm or bad.

How does adding an opposite as “fast where we are slow” specify anything?

It emphasises that the contrast is the thing of interest, rather than the properties themselves.