I don't know what you've been reading Frederick, but in the thread for chubby men there is plenty of love for larger than average BM from quite a few of the ladies here. In fact the majority of the regular female posters have indicated an open mind when it comes to physical characteristics, so I'm not sure where you're getting that they only think 'dudes with 5% body fat are good enough for them'? As a general rule referring to women as 'broads', and anyone as 'obese' or 'fat' isn't going to be met with a positive reply. Even if someone was overweight, I would never tell them they were fat, that's just mean spirited. Like I said you can voice your opinion and make your point without being rude.
You also shouldn't assume that because someone supports a person being any size they're comfortable and happy with that it means they themselves are overweight. IB for instance is not someone who would be considered obese or fat.