Why would being around straw-hat make Ichigo lose his faith in humanity? And why would a shinigami point this out in this situation?
It's a good point, seeing as the Squad Zero as well as Urahara, or even most of Ichigo's enemies, were not human... the only reason he could have lost his faith in humanity, might have been because of the Fullbringers... . Still, they are human-like, and have human nature, so it can be pardoned .
A real Colossal Sword, is only Colossal when it is at least 5 times bigger than the thing you pilot: