AITAH For Freaking Out When I Caught My Husband Looking at School Girl Hentai

This happened two nights ago now. At first, I got up (he stays up quite late and I don't) to see when he was coming to bed. I jokingly asked him if he was up watching porn. Now for reference, porn is openly allowed in our household, as well as masturbation. I have no problem with either. He initially told me 'no' but looked slightly clammy, so I pressed further. Maybe this was my mistake. He claimed he was reading text posts about incest, which isn't necessarily a bad thing to me (depends on the context). So I asked what he was reading and he cracked further.

Turns out he was reading schoolgirl hentai. At first, this didn't bother me very much, until I saw the porn in question. She looked about the age of 13 to me. Given it was a drawing, he says because it was a drawing he was not hurting anyone. But I just can't help but feel sickened by the contents of what he beat off to.

I told him this changed the way I look at him and that he needs to make better judgment calls on what he consumes as porn. He agreed that he does and that he won't look at that kind of porn again if it bothers me. He also claims that this comic was on the first page of the hentai site he was using. But I just have a sinking feeling in my gut that if he's willing to lie now, he'll be willing to lie in the future. AITAH for letting this get me and treating him differently? Is this a huge red flag for other behavior, or am I just overreacting?