I think I sort of covered this in the rest of my post, but the reason is because Mitsuo is at least active. Even if I don't have the evidence I need right now to prove he's scum, I might be able to if I keep him around for a while longer, or he might find a way to prove that he's town.
Hanako, however hasn't said anything. I have no way of getting evidence of her being a scum, because she doesn't post. The last thing we need right now is less activity. And, I find her silence to be a bigger threat right now, especially because Igor doesn't seem to be looking for a replacement, (unless I missed something in the discussion thread), though maybe I'm reading too far into that.

Note: Sorry it took me so long to get this short post out. I'm trying to multitask and it isn't going well.