I concur with the general points about grey areas, and individual children, etc. I don't know many out-and-out doormats or rebels as adults, but I do sometimes get a bit hot under the collar if I'm told what to do when I think I'm doing fine without help. I do remember feeling terrible guilt and shame about the way that I had different identities with my parents/friends etc. and I think that is in part related to how 'unacceptable' behaviour was dealt with in my house.
There are a couple of reasons that I liked Unconditional Parenting (which is what the article seems more or less based on). First, I do sort of wonder about 'consequences' because this so often means things that the parents have made up as punishments - losing a toy, or whatever. The real consequences are why I don't want my DC doing the 'no' list (biting etc.) i.e. the effect that it has on the others involved. So in that sense I'm against (abstracted) punishments.
Second, I don't like time-outs because I don't want my DC to conflate what I think of their behaviour with how I feel about them. I don't want to give the message that the child is unacceptable to me (and therefore must be removed from my presence) unless he or she is behaving in a manner pleasing to me and also, if the child is removed, I can't deal with whatsoever overwhelming urge/ emotion is producing the behaviour (which seems to my mind to be the most important thing to be addressing). So I'd rather stay with the child and intervene in the behaviour, point to its consequences and attempt to understand where it's coming from.
I don't see things like self-discipline being in conflict with a more relaxed approach - I think it's my job to help the child see the big picture and find their own intrinsic motivation for practicing their instrument or attending their dance class, and that motivation should be unrelated to praise or threats etc.
I have also seen many examples of bad behaviour in children and young adults. Much of it seems to be around a lack of consideration for others - which I don't think is implied by Unconditional Parenting, and more still seems to be around impulse control/ children unable to handle their more unpleasant emotions effectively and without acting them out. Again, this is not something that I see implied in Unconditional Parenting.