What shocked me with Taichi's speech was more the words he used, rather than the reasons why he is lashing on Himeko.
The subs don't really show the extent of what Taichi said (considering how clunky it would be in English), but I think the point should be addressed:
Literally, Taichi said something like "I didn't think/expect you to be a human of such level". Unless I'm mistaken, "
その程度の人間" has a very strong derogatory vibe that is more than just "blunt". The fact he used 人間 (human) instead of 人 (person) is quite something (pointing the living being instead of the individual).
It basically put the person in another "category of human", which is more than just saying someone isn't sharing the same view, or being "inferior": it places them in an outright different league (emphasis with その, making the gap between them "bigger" than with この), and sometimes can be taken as "not human", if you pick extreme cases. The "なんて" part also adds the context that "you didn't expect that", as if the asserted point (that Himeko would be such person to abandon her friends) never crossed your mind.
That kind of expression is quite insensitive, considering you simply put a standard on yourself (as human) and that the person in front of you literally fails to meet these, or if you want to look at the other way, that you can't recognize the person in front of you as the same "human" as you are.
I know that Taichi was under the effect of the "desire unleashed" issue, but the way how Taichi has "expectations" for Himeko (and prolly for others) shows how much Taichi isn't really normal. At this point, I agree with people that Taichi's selfless righteousness will be a major issue in the future, leading to either self destruction, or putting people on a weird piedestal until they "disappoint" him.