Maybe because he’s a great actor? I mean he’s really good at pretending to be lots of things for some reason.
Neeson’s thing seems morally different to me. First, he volunteered it, rather than being caught at it. Since he could effectively never have been caught (it was entirely in his head), why would he volunteer it if not to make a confession and expression of remorse about it? He clearly feels / felt guilt about how he was and felt some compulsion to come clean about it. I’m pretty sure we’re supposed to have some reaction beyond revulsion at the original impulse.
Second, he isn’t denying or minimizing or otherwise trying to mitigate it. He’s owned it, for good or ill.