SALT LAKE CITY – A series of graffiti-like paintings on rocks in national parks across the West set off a furor on social media this month, angering people who say they desecrated some of the nation’s most famously picturesque landscapes. They’ve also created a headache for park managers who have the delicate task of cleaning up the sites without causing further damage. It won’t be easy to get rid of the paintings, photos of which were posted on Instagram and Tumblr and then picked up by hiking blogs.