Thus if the root is bad so too is the tree. And if the tree is bad (e.g. the deplorable condition of art and music in the West today) then the cause is a problem with the roots. Part of that problem is evolution, which because it makes claims about (or at least is logically applicable to) metaphysical matters of the kind addressed by philosophy and religion, impacts the arts, politics, and other parts of the tree in a negative way.
Many argue that evolution shouldn't be applied as it is, but that's inevitable for a system which claims to supply an alternative source of ethics. It won't just be limited to changes in populations, as some have suggested in this thread. That's not how human nature works.
People don't want to be told what to do by higher authorities (even when it's in their own good: e.g. parents telling children not to touch the hot stove), so when someone comes along and offers a theory that seems to explain the world without a troublesome God who tells us what to do, it's natural that many people will embrace that theory and apply it beyond its original imagining.
All philosophies work that way, and seeing negative unintended consequences is one way to confirm that a philosophy is bad. Marxism, for example. Lots of people are still trying to find or apply a purer version (it was corrupted in the Soviet Union, China, etc.), but they don't want to think there just might be something wrong with the theory itself.
It's fair to test evolution in the same way: what are its fruits when applied, however imperfectly or however impurely? One certain fruit is that the individual should be subordinate to the species. Millions may die if humanity progresses as a result. We could wait for millions of years, for weaker races to die off slowly, or we could take the next evolutionary step and apply brainpower to accellerate the process. The latter is the approach taken by the former Soviet Union and early communist China. Pointing this out isn't an attack, just a note from the historic record.
The burden of proof is on those who would tell us not to extend the application of evolution to such logical consequences in society or, alternatively, show us how those consequences aren't logical.
Evolution does no such thing, and I would vehemently disagree with anyone, proponent or opponent, that says it does. All evolution purports to show is how species evolved from other species. It could, speculatively, accomodate the development of a moral or aesthetic sense in humans, but behavioral genetics is in such infancy as applied to humans I'd be doubtful about any such extension. We don't really know what aspects of behavior are innate in humans, so arguing how some human behvior evolved is premature.
If people choose to inappropriately deduce moral conclusions from evolution, which I would argue is just another example of the 'naturalistic fallacy', that's no more a valid criticism of evolution that analogous deductions that 'everything is relative' reflects on the truth of relativity, or that 'no matter what you do, it affects what you're looking at' reflects on the Heisenberg principle.