WHATEVER view one takes of R. Kelly — that he is obscene, insane, outlandish, played out, musical kingpin or joker — one thing is irrefutable: America deserves him. Five years after being indicted on charges of child pornography, dozens of hits into a career spent raunching up R&B, Kelly's enjoying yet another climb up the charts with his eighth solo album, "Double Up." Defenders of morality and good taste must wonder how the honey-voiced potty mouth remains so successful, or at least hope that his flamboyant tastelessness represents the endpoint of sexually explicit pop.