So yeah, if you want to defend Zen, you do it by showing me what good Zen has done. Debate about what is "good" Buddhism, postulations, and convoluted philosophical talk won't change my mind when I look out my window and see junk practitioners who might as well not even know the word Zen because it hasn't benefited anyone.
I am presently a student at Komazawa University in Tokyo. It officially belongs to Soto Zen and includes a seminary and large Buddhist studies faculty and library. So, perhaps I have some authority to speak about modern Zen in Japan.
To say the least, Zen Buddhism in Japan is a bit different from Zen Buddhism in the English speaking world. To be honest, there isn't a lot of crossover between the two except for a few celebrated individuals. One might go for a trip to Eihei-ji, but unless you speak Japanese very well they'll just treat you as a guest and you'll not really "get into" the organization so to speak.
Anyway, modern Zen in Japan is a far cry from what it was even one hundred years ago. There is little regard for precepts and such consumption of alcohol and killing pesky insects is not an issue. There is not much of a "karmic consciousness" (constant awareness of karma) as so far as I've observed. A lot of temples are just inherited funeral businesses that people get stuck with as monks marry and pass their robes and property to their children or more usually a single son.
It is odd because if you read Dogen for example he talks quite clearly about karma, rebirth, the need for precepts and a lot of other topics which for Buddhists should be axiomatic but in our present day are not. He scolded monks for having a closet for private possessions. He insisted on just having robes and a begging bowl. Anything else was extravagant.
That sort of lifestyle is the stuff of legends nowadays. If a Japanese monk just abstains from meat, doesn't have a girlfriend and never drinks alcohol, people will think he's quite amazing and exceptional, meanwhile next door in Korea or Taiwan that's just the basic expectation of how a monk should conduct himself. You don't get bonus points for not eating meat -- it is just common knowledge that monks don't eat meat.
Needless to say there are a lot of problems and I think Soto Zen along with most of Japanese Buddhism is in a rapid state of decay. The number of Buddhist priests and temples has decreased significantly in the last few decades and the trend will continue. Japanese society doesn't care about Buddhism anymore. There is the odd person who likes the literature, but the perception amongst anyone younger than the baby boomer is that it is an archaic funeral service.
Now, that being said, Soto Zen invests a lot of money into the scholarship of Buddhism. Not only Zen, but even Tibetan, Sanskrit and Pali studies as well. They also host discussions on human rights and so on. They're generally all good people. However, there is a lot of apathy about Buddhism. Religion in Japan takes a secondary role to the demands of society and culture. The latter are by default nihilistic and materialistic in their ideology. Conformity being a virtue in Japan, it is best to tow the mainstream line regardless of what Shakyamuni taught.
The Zen Buddhism you probably are referring to is the English speaking Zen.
For various reasons, it tends to be readily warped to suit the tastes of people. Rejection of rebirth and karma are the obvious examples. The fact that anyone can write a book on Zen and have it sold alongside books by elder masters like Ven. Shengyan or HHDL is disappointing.
What I see going on is that Zen in America for example might have a few Japanese priests hanging around, but they themselves come from a culture of apathy towards actual practise and preservation of Buddhadharma, so there really is nobody to say the warped versions of Zen that are arising is wrong. You have a bunch of people with a half-baked adaptation of Zen selling it (and it is sold in many cases) and few would know how poor the product is.
Case in point:
Here in Japan, however, almost nobody knows about this kind of nonsense. They also wouldn't care.
In the case of Theravada, Tibetan or Chinese lineages, if someone tried to do the same thing you'd have a sharp response from a large community of dedicated elders who actually believe in what Shakyamuni taught. With Zen you can just get away teaching anything you want because the organizations themselves back in Japan just don't really care.
I think there might be a parallel between Yoga and Zen in that Zen as it went abroad likewise lost its spiritual significance and it became a simple exercise and lifestyle from the exotic East.