As someone who works with disabled people I can see how  transhumanism is a seductive ethic.  However the "I wanna live forever" principle (apart from being the basis of many dreadful songs and more than one socially controlling religion) throws up the more practical question of ...Where do we put everyone when immortality becomes the norm? Further, interactive brain operated computers can be virused and accessed externally...or perhaps that is already happening. However, in such a morally complex debate as this it may be easier to take the line...if Fukuyama sees this as a bad idea then it must have its virtues.