FFS, no-one's saying that anyone is too heavy to fly, rather that they're going to actually weigh people rather than using average data that is obviously way out of date as people have got taller and heavier, to improve efficiency and yes, increase profits.
It's all very well weighing luggage and charging extra, but somewhat pointless when people vary in weight far more than the average suitcase.
It's all well and good using an average, but what happens when the passengers on the plane aren't average?
Eg when a lot of them have come back from 2 week's AI and are a stone heavier than when they set off, or if there's a large group of different nationalities that tend to be much smaller or larger than an 'average' person, or there's a rugby team on the plane and they're all large, muscular people and hence heavier than average.