It's also worth considering that Joyent is likely feeling threatened by Docker picking up unikernel wonks, because until now Joyent has been able to keep Docker in a "containerization and deployment" box, competing on other things in SmartOS and other parts of their stack. Now Docker is pretty plainly coming for more of their pie (with the winds of "hot new valley thing" behind them, which Joyent distinctly lacks), and this wouldn't be the first time Cantrill has blogged out of feeling threatened or angry.

I don't agree with minimizing arguments based upon personal opinions of the author. Please don't interpret my comment that way. I'm just pointing out context, which is worth considering when evaluating the arguments.