The added stress isn't very significant, and doesn't surpass what a coral might face in the wild. Remember that if you are using 10 - 20k bulbs, you are already showering your corals in some UV-A light. This is part of what brings out their fluorescent coloring.

Producing the pigments to deal with this light is part of their normal energy budget anyway, and so I choose to let it happen.

In the end, it's purely a personal preference. I enjoy the bright blues that get produced by my (formerly) green brain corals.