The scope of this cause is so huge though, this is the next Era of humanity, that we will just bowl right over the critics and resistance once we pick up enough steam.
That is precisely why it is more than indefinite life extension. The power to alter our course as living beings from that which we have been given by consciousless environmental factors is a very large question to handle. From this point, the idea is self-modification. How do we view ourselves in relation to the rest of the world? If at first we are given the power to grant longevity, what is next?
I think that what Immortalists and even Transhumanists face is a sort of phenomena that might be expressed as a second advent of self-awareness. Rather than when one looks into the mirror and sees the body they have been assigned by chance, and discerns their conscious relationship with it through hand-eye coordination and later into the complex network of society, one looks first at the world around them because this is the new source from which awareness must come. The change in the technology we operate from comes from the developments around us, not necessarily from within any longer.
The roles we are given in life are no longer granted by predominantly environmental factors, they come from societal factors. *Shock* suddenly, there are unknown elements within everything. The physics of the environment is an easy and tame situation to model in one's mind. The physics of society and meme construction is something of dreams.
Unfortunately there are many out there who seek to take advantage of this second awareness and sleeve this unknown world into packages labeled with memetics which are either outdated or riddled with useless world sentiments. Which is why I think you will find resistance to the suggestion of Immortality/Transhumanism firstly, and secondly because of the uncertainty factor of self-modification as a capability of societal physics rather than environmental.
Identifying new fundamentals about life, where previously more easily identifiable (food, shelter, virtues identified by Plato *which generally carry into today*, etc) which will be consistent during the singularity are essential. I don't think the nature of human behavior will favor the idea of serving a bunch of Optimus Primes (some of which are modeled after the minds of people who sought this powerful state of being so vigorously) and living eternally under a Grandfather Law, even if some choose cybernetic enhancement.
The question I'm about to ask I see as inherently a matter of two societal paradigms and the relationship between two technological paths: collectivism and individualism (that is values which are manifest through a single vessel within a larger society, or values which are manifest through multiple vessels as a whole (respectively)), biology and technology (the first of which was a development of the consciousless environment, to which we have no ruler but the inherent rights of men/women; the second which is a development of a conscious environment, where we have seen infinitely more destructive developments than the largest of storms and droughts)
So I'd like to ask you, what is the value of an individual within our present and projected future society? More specifically, do you see a role for biological life in the future which (presumably) would welcome it's longevity?