Is AUTHOR wrong in the post ? POST : Hey guys, and this is a tough one for me as everything is still very fresh and painful. 
So for some context: I am a 28
yo large and tall woman, have been in what I assumed to be a serious relationship with the 35 yo man for the past year.
My ex has been obese most of his life. When we met (online), and added each other on Facebook, I looked through his photos (obvs) and noticed an obese man standing next to his mother who I assumed to be his older brother/cousin.
Imagine my shock when N. told me it was actually him! Apparently by the age of 21 he got so morbidly obese that his condition became life-threatening and he got a gastric bypass. Now he is super-skinny as he eats a tiny amount of food (less than a handful or smth). 

When it was the first time we were about to have sex he refused to take his clothes off, and I reassured him that I could handle whatever he would throw at me. Eventually he undressed and I realised why he was so nervous - after the surgery he was left with loads of loose skin that he didn't have the money to remove. There was so much extra skin around his waist that it completely covered his genitals. Since I was deeply infatuated with him, I did not think twice. If you want a man, you accept all his flaws, at least physical.

Sorry for the long intro, down to the story: we had been having problems for the past few months in our bedroom. As in, he hasn't attempted to touch me for two months straight. Eventually I got really frustrated and self-concious so I ranted on r/sex. Folks gave me some decent advice and I decided to talk to him about it.

Well, the convo didn't go as I planned. Eventually N said that two months ago he met this fit sexy 19 yo at the bar, and she hit on him and he had to say that he was taken, and she seemed to be very upset. And this incident made him think about our relationship. According to him, despite shedding over 200 lb of weight, he still had "a fat man's mentality" and "settled for a big girl because of his lack of self-confidence". To that I started crying histerically. He then said that our relationship can be saved if I "make a concious decision to beat myself into shape" as he realised (after a year of sleeping with me) that he is not sexually inclined (sic) towards a woman with cellulitis. 

 I was at loss for words. As an overweight (but not anywhere near obese) woman I am constantly on guard, I'm eating healthy and have an active lifestyle. N., on the other hand, lost weight surgically and retained all of his unhealthy habits (he eats only unhealthy foods, hates greens and holds any healthy options in uttermost contempt) but since he's eating micro amounts he doesn't gain any weight. 

I replied that I am constantly dieting but no matter how much I do I will never become a skinny petite 19 yo he met at a pub.
To that he replied sceptically that all I have to do is to eat tiny amount of food just like him! It's so easy to lose weight if you eat as little as him!

Now, guys, this blew my head off. I yelled at him: If if it were so easy to eat tiny amounts why were you so morbidly obese by the age of 21 that your life was in danger? 
And also something like: how dare you give reccomendations to me, a woman who is super-concious of what she eats being a man who has never done anything to lose weight, acquired zero healthy habits, whose weight loss was achieved only by a surgeon's scalpel?

Of course he took offence and stormed out of the house. He has been with his mother for the past few days, and there are dozens of angry texts on my phone from his mum and sister. They are calling me names and saying that N is depressed because of me, and that I will most certainly burn in hell. At the beginning I felt justified and self-righteous but now I'm feeling assholy. I fell really low but I could have fallen lower, I could have told him something about his loose skin but thank God I did not.

Guys am I trully an asshole? Sorry for the long and incoherent read. I'm a bit of a mess!

TLDR Previously obese boyfriend with gastric bypass breaks up with me on the grounds of my weight; I call him out as a person who has never done anything to lose weight apart from a surgery.