I'm not all that sanguine about street art on other people's property to begin with. Sure, something really artistic on something blighted, that's easy to aesthetically justify. Defacing something that had its own beauty of place and aesthetic intent? That's rude, at the very least.
Extending that to national parks — something preserved with aesthetic intent, and owned by everyone, myself included, the tagging of natural features (or even artificial structures) is a sketchy thing to do at best (so to speak), but it also has a "broken window" effect: even if someone's art is the greatest thing since Alma-Tadema, violating that social convention opens that space up to art and messaging that simply won't be.
As to the sentiment, "If provoking outrage is not part of your intention as a graffiti artist, why do it?" … well, that just sounds like you're being a dick, not an imp or gadfly.
Graffiti artists’ move to national parks shocks nature community
Andre Saraiva is an internationally known graffiti artist. He owns nightclubs in Paris and New York, works as a top editor of the men’s fashion magazine L’Officiel Hommes and has appeared in countless glossy magazines as a tastemaker and bon vivant.
During our hike in the Picketwire canyon we stopped to see 1500 year old petroglyphs on the canyon walls, but several someones decided that those weren't worth looking at and destroyed them all with their own carvings.
+Stan Pedzick Words fail me.
+Dave Hill it was very anger inducing.