There are a few reasons, but I don't know him well enough to actually take a real guess.

[And while he can speculate, and as annoyed as he is at Akechi, this is also a teenager with clear emotional issues and so it feels out of line to just be throwing out those possible reasons without enough evidence.]

But people don't usually get that malicious without some sort of reason, and if it isn't because he likes and wants to defend you, then the next most obvious reason seems to be that he wants you to dislike us. And maybe I'm wrong, but it's something you should be aware of.

[And therefore possibly take his accusations with skepticism.]