You said: That 1) humans will lose part of their humanity, 2) how they'll achieve it (the ends don't justify the means), and 3) it's a bad idea for a reproducing species (with a reproductive rate as relatively high as humans) to 'live forever'. And it's doubtful everyone will be happy. Happiness isn't defined by how healthy or wealthy you are. I see your opinion as a bit simplistic. (And I haven't a clue what the verse you included in your post has anything to do with this).
First the verses. If you go to verse 34 of the chapter I referred to, (Acts 5:35-39), you will see the speaker is Gamaliel, a Pharisee, and very wise man. The counsel in Jerusalem were planning to slay the desciples for spreading their dangerous heresy. It was to this counsel that Gamaliel spoke. His argument is essentially this, if this apparent heresy is really of God, than to fight against it would be to fight against God, but if it is really a heresy, God is not in it, and it will go nowhere. It is better to do nothing.
It is the same with these Transhumanists. Most of what they propose is simply science fiction and being afraid of it is like those who were afraid of a Martian invasion after Orson Wells made H.G. Wells War of the Worlds into a good radio program. 'It ain't gonna happen.'
Certainly science will find new cures for disease, prosthetics will be improved for those who need them, new technology will continue to improve the lot of man in every way, but the grand scheme these guys are dreaming of is impossible.
But, supposing it were possible, and it did happen, what in the world do you think could be done to stop it?
Now your points:
humans will lose part of their humanity... Nah. The specific aspect of human nature that differentiates humans from all other organisms is their rational/volitional nature, that is, the necessity and ability to live by conscious choice. Except for his means of reproduction, almost no single aspect of a human being is necessary to human nature. If this were not true, we would consider people with handicaps or other anomolies non-human or less than human, and we do not. As far as the rational/volitional nature is concerned, that cannot be changed at all or it ceases to be altogether.
Besides, philosophically this is impossible. A thing is what it is, that is, whatever nature a thing has, it has that nature and no other. If you change the nature of anything, it is not the same thing with a new natue, it is a different thing altogether, even if it is very similar to the original.
how they'll achieve it (the ends don't justify the means) this fear cuts both ways. Of course, immoral acts are immoral acts, regardless of the objective of those acts, but that is true as much about those who want to stop the transhumanists from pursuing their objectives as it is the transhumanist objectives themselves. How do you intend to stop them? The ends do not justify the means?
it's a bad idea for a reproducing species (with a reproductive rate as relatively high as humans) to 'live forever'.... I'm not so sure cyborgs are all that interested in that activity that results in offsping anyway, so I wouldn't worry about this one.
And it's doubtful everyone will be happy.... Probably true since they are certainly not happy now.
I see your opinion as a bit simplistic. Well, this is only a forum, and I've discovered in depth explanations are usually misunderstood (as you misunderstood my allusion to Gamaliel) or ignored. Nevertheless, the criticism is correct. This post is implistic too, by intention.
Hank