"...Yes, it was a kind of adultery, but at the same time Jean wasn't being his wife anymore."
You can call it something other than philosophy, if that helps. It leaves a bad taste in my mouth, regardless.
And, yeah, there ought to be some leeway between a one-dimensional "ideal" and a character marketed as a hero behaving reprehensibly without much self-awareness about it. This isn't an example of using that leeway effectively.
X-Men as 7th-rate Pinter with explosions is fine if that's what you're into. It's just not what I'm into. Hell, let's get Sondheim in here. At least then the scenery and costumes won't be such an eyesore. Oh, and there'll be catchy tunes, too.