Definitely not, majority of the time there is no excuse.
As though everyone undergos a choice one day where they say "i'll pick skinny" or "i'll pick to be fat".
Go find a fat person who grew up overweight, got bullied because of it and was never taught proper eating habits / relied on food for comfort etc.
I'm not saying they can't or shouldn't change. But there is no single moment they should have to have an excuse for, it's simply what life was for them. That's not their fault.
You can debate each time they chose to eat too much or the wrong thing was a choice, yes, but for most i think surely there's a point where even if they know its wrong, it's the only option. They can't even possibly begin to imagine the years of hard work required for them to lose it.
The mindset of people who have been skinny their entire lives probably cannot even begin to emphasize with someone who has a lifetime of bad habits to fix, or that of someone who cannot walk without getting tired.
Again, not saying people should chose to be fat, or that they shouldn't fix it. Just that everyone here is seemingly of the opinion "fat people are pratically the devil! they do it to spite us!"
Unless you've lived in a bubble you've taken chances which could have lead you being a burden on society. Including ever entering a car, crossing the road, smoking / drinking or any other hundreds of thousands of activities which could have left you a burden.
EDIT: Fat people eat more. Fat people pay more on food than you, therefore they pay more VAT, therefore they pay off their medical bills. Logic is infallible.