Okay, thank god. The reason why it seems like he's cool with it is because in chapter 32, Ain asks him "Are you upset because you think I lied to you?" and Michelle says "I don't think I was deceived" and that "I don't think everything that happened at the mansion was a lie" while still clearly being uncomfortable with Ain's deception, so it's just kinda frustrating how easily he seems to go along with Ain's manipulation afterwards when literally every manipulative question could be answered with "I'm hesitant because you lied to me."
I think he means he wasn't deceived because he believes the feelings they shared in the mansion were real, he doesn't want to put them into question even tho Ian lied to him because he truly felt love and felt like he was loved by Ain. Michele is very much hesitant even in this chapter and it took Ian basically terrorizing him to make him reconsider the sleeping together thing, but he isn't that easily swayed, he's pretty stubborn in wanting to know the truth from Ian.
I get that that's what he means when he says not "everything" in the mansion was a lie, but even in this latest chapter, Ain/Ian is once again trying to manipulate him by bringing up how "well if you consider me and the servant to be such different people, you might as well just marry my sister, right, because you can't trust me anymore, right," and Michele still can't say "yeah, actually, I can't trust you, and that's your fault because you did lie to me."
I understand there's a psychological scare tactic going on and Michele is currently afraid of what Ain might do to him (which is its own level of messed up), but this is the third or fourth conversation of the exact same nature they've had, and it gets to a point, you know? It's starting to get frustrating that Michele falls for it again and again, hence why I expressed my frustration that he still hasn't managed to even say "hey, it's kinda messed up that you lied," but instead got a nice handjob out of it instead. It feels like we'll be here for another 20 chapters before he musters the courage to speak out.
Yeah, I actually get what you mean. Michele was pretty verbal about this from the moment they entered the castle. He's clearly bothered by the deception even though he doesn't believe everything that happened between them at the mansion was a lie. I think the problem is that Michele and Ian are almost talking past each other. Michele's hesitation is basically, “You deceived me, so of course I'm confused and unsure right now,” while Ian, because he still doesn't trust Michele's sincerity, interprets that hesitation as further evidence that he needs to keep testing him ( ̄∇ ̄"). Btw, Michele isn't actually as much of a pushover as he might seem right now.

How is Michelle not just all "Hey, so yeah, I don't appreciate being lied to. You say you love me, but you also spent a month telling me you were a servant preparing me to marry a lord, which was a whole-ass lie, so you loving me could also be a lie. I don't know you, I don't know when you lie and when you tell the truth. How about we start from there?"
Like bruh, how is he so cool with that whole thing?? I get that Ain is being manipulative and "Oh do you think I deceived you? Are you unhappy to find out you have to marry me, after all? :(" and whatever the hell, but I really wish Michelle wasn't so spineless so as to straight up just call him out for lying.