I think body positivity should be aimed more at fat men than fat women

I'm going to have to strongly disagree on this one.

"Fat women can still find a lot of sex,"

Eh, maybe but it's often them being fetishised, just being used and/or all too frequently treated as a joke afterwards. In fact, it was just in the news that a fraternity at an Ivy league school had a game going where you got extra points for sleeping with fat women and this is hardly a rare thing, in various forms and degrees it's pretty common in real life and is also the plot of countless books, movies and TV shows. I can't think of one example of this for fat men.

And fat men definitely do get laid.

"and even have a porn category for them (i.e BBW)"

That's not a plus for the women, it's fetishising and porn is (mostly) made FOR men so it's not surprising that there's categories for what men want and not much for what women specifically want since they're not the main consumers. Also, there's a loooooot of fat men in porn, in all categories, while the fat women are mostly stuck in one category.

"and are considered desirable to an extent for some men."

Plenty of women like overweight men. I'm one of them.

"Fat men on the other hand are virtually seldom sexualized,"

That's not really a bad thing. They're seen as human beings.

"and are usually just mocked at."

Not more than fat women.

"Very few women consider them attractive."

I don't think that's true if you consider all age groups. Yeah, you might find fewer very young women who find fat men attractive but for a good portion of women, that becomes less true with time.

Some other points...things that happen a lot to fat women but not really to fat men:

-guys hiding their fat girlfriends from friends and family out of shame.

-it's much less ok to be fat on TV. Look at a staggering number of sitcom couples...fat man, beautiful slim wife. From the Honeymooners to modern shows, it's extremely common and the inverse is almost unheard of.

-it's less accepted to joke about being fat while men can definitely do that. A lot of the time its more like fat women are made fun of and silenced while men can use their weight to be funny. (Ex: Chris Farley, Gabriel Iglesias, Ralphie May, Jim Gaffigan etc, no real female equivalents). Not that it hasn't been attempted, it's just not well received.

-getting dumped for putting on weight, happens to both but it's more common for women and there's way more pressure to stay thin.

I do think you have a point.
1. There has been an effort to show sexier fat women and slightly heavier a.k.a. "plus size" female models. Fat men are still seen as comic relief and plus size men's clothes are usually modeled by lean buff guys.
2. There are so many stores either just for large women (like Lane Bryant) or recently extending their sizes (like forever 21). There is only Casual Male XL. Also, Walmart features their plus size women's clothes IN THE STORE. As for plus size men's clothes, there is tiny lettering on the shelves telling you you go on-line to buy plus size men's clothes. WTF? Don't tell me there are no fat men in Wal-mart.
3. Lastly, in response to WIGZ, I DO know of cases where women have hidden fat male lovers out of shame.
4. While BBW attractions are controversial because men are fetishizing women, there is a double-standard about men and women having fetishes altogether (with the exception of BDSM). It is more expected and depicted that men have fetishes than women. If a woman dates a fat man seemingly for solely emotional reasons, she's is considered a deep and kind person. If she dates several fat men or appears to have a "fat fetish" people become unnerved and creeped out.

There's a lot of fat guys I know that manage to get good looking thin women. I don't think women seem to consider a guy's looks as much as guys do with women. And there's certainly a lot more shame thrown at women for being unattractive than there is with men. I'm not saying that therefore we should disregard the men that do have low self-esteem from their perception of how attractive they are, their problems are as important as women's, but women do generally have it worse.

Could you please explain this "body positivity" that you wish to encourage for fat men?

It it a pat on the back & a softly spoken "there, there" that you want from ordinary passers by? Or do you want people to wear badges & t shirts with 'Fat men matter' on? Do you want popcorn scattered in front of you as you walk?

I saw a big brown pile of dog shit on the ground today at the park. It looked pretty fresh too.

what u talking about fat guys are hot, also check deviantart if you wanna see sexualised fat dudes!