A viral showdown between social-media philanthropist Damon Darling and Walmart is raising questions about where charitable giving ends and store policy begins. Darling, who has millions of followers, became known for paying for strangers’ groceries and giving away cash at Walmart stores. But after a confrontation at an Ohio location this month, Darling was served with a trespass notice and says he has been banned from Walmart stores nationwide. Reports also say the ban includes Sam’s Club and Murphy USA locations. Darling’s supporters accused Walmart of punishing him for helping customers, and some called for a boycott. But Walmart says that is not why Darling was banned . The company says the decision was based on repeated violations of store policies, including disruptive behavior and trespassing, and was unrelated to his charitable giving . Reports also cite previous prank-style videos filmed inside Walmart stores. Darling has taken a different approach from some of his suppor...