A free market doesn't require people to weigh the costs and benefits of others. The whole wonder of a "true" free market is that is that, in such a market, everyone can act purely in her own self interest and collectively produce an efficient social welfare outcome. Of course "social welfare" is defined in terms of economic agents preferences here so, even in a free market, if people have preferences that don't jive with their actual welfare (basically what you're calling uneducated consumers) you can still get rather perverse outcomes.

The real issue here is that the environment is a common pool resource.