It's a perfectly reasonable conclusion.
While this may be true, it does not follow from your saying. Chaosmage is concluding p (google is more trustworthy), while CellBioGuy is concluding not-p (google is less trustworthy). If you look at the actual definitions of modus ponens and modus tollens you'll find the following:
Modus ponens: A -> B and A, therefore B
Modus tollens: A -> B and not-B, therefore not-A
In other words, CellBioGuy would've had to conclude the negation of chaosmage's premise (and not his conclusion) for your saying to be relevant in this situation.
There's a double implication involved: "Google is trustworthy if and only if transhumanism is worth taking seriously." (Or at least the probabilistic version of that.) So there's four possible Modus Whatevers to use, and I think altogether we've covered three of them. The remaining possibility is "Well, I took transhumanism seriously before, but if Google supports it, then it must be nonsense."
It makes a lot of sense for the Google people to be transhumanist, with Sergey Brin and Larry Page working with the Singularity University, but still I was surprised to hear this on the new Colbert Report (of the 23rd of April):
He seemed quite serious, too.
I guess a lot of people would take transhumanism more seriously if they heard the top people at Google are in. To me, I actually find it makes Google seem more trustworthy. In-group psychology is weird.
Here's another good interview with Eric Schmidt. No explicit transhumanism, but some fairly intense plans entirely compatible with it.
(edited: corrected title)