It's a rhododendron disease from the Netherlands. You're right, that this is Darwinism in play, but it's due to human influence. So human intervention is no more artificial than the original evolutionary pressure.

It just depends whether we value preserving diverse ecosystems, or if we're happy to spread species / diseases around the world and just see what survives. I'm not saying there's a fundamentally "right" answer, but I prefer diverse ecosystems to the point I think it's worth trying to intervene when possible.