Madonna considers a lot of people to be Rebel Hearts, but at a concert Tuesday night, she paid tribute to the man whom she considers to be the first rebel she laid eyes on, David Bowie. She was one of the many celebrities to post tributes to him on social media, and, “He was one of the geniuses in the music industry, one of the greatest singer-songwriters in the 20th century,†she told the crowd in Houston. “He showed me it was okay to be different.†Rock on, hot tramps.