I think the point trying to be made here, isn't that "I just don't want too" isn't a perfectly valid reason, because it is, but that "I just don't want too" pretty much every single time is also a perfectly valid reason for a husband to get pissed off, feel like shit, and want to leave or at least recognize the issue.

If he's not happy with his relationship, because he's not getting enough sex, and the excuses being given are clearly just the first thing that popped into her mind, there's a number of things I'd be thinking. 1) Is she cheating on me? 2) Does she still love me/find me attractive? 3) Why is she not telling me the truth, the real reasons she doesn't want to sleep with me? 4) If I bring this up and talk her into having more sex with me by making an issue out of this, how awkward will that make it every time she says yes and I know it's only because I brung the issue up.

I mean, it's a two way thing and we don't know all the details, far from it, but the two different ways this could go is, maybe he is a cunt and treated her poorly, which is why she's not having sex, in which case she should really bring it up and even end it (depending on how poorly he's treating her), or she is not being fully true to him, in some way or another, either in her reasoning or even in the bedroom, in which case he should never speak to her again. I'd never go back to someone that lies and cheats. Never.

I mean there are other ways this could have gone aswell. We just don't know. But I also disagree that sex isn't a necessary part of a relationship. If I fall for someone, and we fuck alot, and then as soon as we get married we stop fucking, it's like, she's changed. She's not the person I fell for. It's her choice, of course, don't get me wrong, but she should be completely true with him as to the reasons, and she should let him know that she still loves him. It's the same vise versa aswell. Relationships are two ways, give and take.

Tl:dr, whatever the couple in question did, I think neither partner where in the wrong. If he's not happy with the amount of sex, he has every right to bring it up as an issue and/or leave. If she doesn't want sex, she has every right not to give it, but she sure as hell can't moan when he gets upset with the fact.