I like the way you present this, Boogie, because it's so true to your style and who you are, and with any luck it may even reach a hater or two.
My personal opinion is that you don't go far enough in asserting your rights and your value, and that of other fat people. Yes, fat acceptance is about accepting yourself. That's a fundamental part of it. But it's also about more than just that. It's also fundamentally about the right of all people to live their lives without suffering unethical institutional discrimination. Fat people are discriminated against at every level--not because of the quality of their character, but because of their body composition. That's WRONG, period. Self-acceptance against a culture of hatred isn't enough. Bigotry needs to be fought back against. It's the haters, not fat people, who need to be publicly shamed and cowed into biting their tongues when they're on the verge of acting out on their discrimination. As a society we've begun to acknowledge this when it comes to sexists, racists, and homophobes, but we haven't quite gotten there yet when it comes to fat-bashing bigots. But we will get there, and that's what the fat acceptance movement is about. It's okay to say that. It's okay to say that you and all other fat people are worthy of that basic dignity. Because you are.
And so, I think it's okay that this backlash against fat people is happening. Because you're right that the cause of the backlash is because of the growing popularity of the fat acceptance movement. Backlashes like these always happen when societies change into something better. To this day there are backlashes against women's rights and minority rights from people who refuse to accept the changes toward equality that our society has made. The backlash against fat people is a sign that the tide is turning for the better, that the haters are on the back ropes and are lashing out against the loss of their immunity to be despicable creeps to other human beings.
The one thing I disagree with you about is HAES, and your belief more generally that being fat is unhealthy. At your size, yes, it's true. You've got a lot of health problems, some of which have to do with your weight. But the vast majority of "obese" people in this country are not 500 pounds. They're 180 pounds, 210 pounds, 300 pounds. At those kinds of weights, it isn't a sure thing that they're unhealthy. You'd have to check case-by-case. And your saying (about there being no fat old people) is wrong: There are plenty of fat old people. Go and look.
In the meantime, you shouldn't assume to know people's health because they're fat. There are even some people--and you're not one of them, but they do exist--who are healthy at 400 pounds, or higher! And not "healthy right now," but healthy for their whole lives, into their 50s and 60s, which is when people of all weights start to develop age-related illnesses.
As for "Health at Any Size," it's a valid and noble movement. It acknowledges that not everybody is going to be skinny, and that this shouldn't stop people from caring about their health. It rejects the lie that people can't be healthy if they're not thin.
This is important because of two things:
First, you yourself said how hard it can be to lose weight. For most people, losing weight until they're not clinically obese anymore is not a valid option. They'll always have that extra 50 or 100 pounds. And that's okay! They can still live healthy lives: They can get enough vitamins and minerals in the food they eat. They can get some exercise. They can go to the doctor to monitor any potential issues that appear on the horizon. And they can accept themselves for who they are, and banish the demons inside their heads who tell them that, because they're fat, they're unworthy. That's the message of HAES. Instead of being burdened with an unrealistic goal of weight loss that they'll never meet, and feeling like that much more of a failure, people can focus on being as healthy as they can be within the body that they've got.
Second, it's important because the vast majority of fat people really aren't unhealthy because of their fat. We tend to think of every obese person as being this 500 pound headless fatty on the news, because that's the way obesity is presented to us in this society. But it's a lie. Like I said, the vast majority of obese people weigh somewhere in the upper 100s or in the 200s. Most people really can live their whole lives just fine with that kind of extra weight. And of those who can't, it's usually because of other health issues or bad genetics, not fat, and they would have developed those health problems anyway. Fat is a scapegoat. If a fat person ever has a health problem, everyone automatically assumes that it's because they're fat. But that's just not true.
But even with the really big people, HAES is still important. For that matter, YOU can be a part of HAES, Boogie. You can start looking at the parts of your life that don't have to do with being fat, and make improvements wherever you can. You probably already do this anyway! And in the meantime, you can continue your journey toward weight loss. HAES doesn't mean "you're not allowed to lose weight." It means you do the best you can with the weight you're at.
Also: I won't get into it here in any detail, but when you explore the medical literature on the subject of fatness and health, you'll find that it isn't the slam dunk that you and most other people assume that it is. "The medical community" may be as single-minded about this as the general public is, but that's not what the science itself says. It's just the telltale sign of a deeply rooted social prejudice. You can realize this for yourself by reading the literature, and speaking to the researchers who conduct it. The truth of the matter is that we don't actually know much yet about whether being fat is healthy or unhealthy. At your weight, Boogie, yes, it's hard to be healthy. But for the vast majority of people, it's much more dubious that their fat is the major source of health problems that we all believe it to be.
I guess the big point I'm really trying to make here is that it isn't usually fat itself that makes a fat person's life miserable. It's the never-ending hatred and messages of inadequacy that people and society broadcast from everywhere, every day. Humans are social creatures and we internalize that kind of bullshit. Like I said, most fat people are only fat by a few dozen pounds. The self-loathing in their lives doesn't come from the fat. It comes from the way that their fat is judged.
When that bigotry becomes unacceptable in our society, fat people's lives will become immeasurably better without any of them having to shed a pound.