One of my mother's friends married a man who was 15 years younger. They dated for many years and then ended up getting married. Her first husband treated her terrible. Her second marriage was the best and age was not a problem. They are both deceased now.
Seriously, as the article points out, the word "cougar" suggests a predatory intent on the part of the woman. But it seems to me that the man in a relationship like Demi Moore's is the predator: out for what he can get from being her beau, and then he'll leave her when she gets too old or too much like his mother or something cuter comes along.
It also seem to me that most older women have few illusions left, and expect that.
Why would you want to call a woman a cougar???
In the same way 50 year old men dating women in their 20s are often referred to as perverts.