We outnumber the humans by far; there are so few of them left, they're now considered rare by the Supers. They're privileged. Wealthy. I've heard that they are given high positions everywhere -- government, business, even in social circles -- simply because they are human.
I think society itself is designed to benefit humans and to give them more of an advantage in order to "even out" the fact that they lack superhuman powers. Their cells also lack the ability to regenerate quickly when their bodies are damaged. If a fire Super starts an out of control fire, I'd burn, but I would heal in a couple days. A human would be dead twice from burns and smoke inhalation. Hence, in both natural and man-made disasters, the human casualty rate is higher. We, the strong, survive and the pure human population thins out.
There are Supers that dedicate their lives to protecting the human race. They're acknowledged among other common-folk 'heroes' like firefighters. We are raised to love them, to respect them, and to want to be them. They call themselves the Heroes, a befitting name for how we are taught to see them. Protecting the last of the humans -- a heroic action!
But in another extreme, some believe that humans are weak, after all, they cannot defend or heal themselves. Our minds are as sharp as theirs, as we evolved from them. Why should we waste our efforts protecting them? These viewpoints greatly contrast the ideology proposed by the Heroes, and so society deems anyone with these viewpoints Villains.
Villains are know absolutely for one thing: help yourself survive. Not humans. Not Supers. Not your family or friends, but only yourself. A 'selfish' but logical decision, as we as individuals, will always always possess a tiny bit of this Villain ideology.