I see your point.
But remember, a great deal of chemicals must be used in the production of real fur...to stop it decomposing etc, much like leather I assume.
If people have a problem with the environmental impact synthetic fibres carry, then they should all stop wearing cotton. It is afterall,
the most environmentally disastrous fibre. Hence the rise in organic cotton use.
Going back to Prada, it is a decision that is addressing one problem, the ethical treatment of animals. It may not be the reasoning behind the decision, but it is a result because of it. Ultimately it is completly unreasonable for everyone to be satisfied by any descision these days, but perhaps we should focus on the positive.
Just a thought...