Politically charged Cho will go on By REBECCA LOUIE Yes, she's a raunchy comedian prone to jokes about S&M. And yes, she finds the Bush administration heinous, to say the least. But no, Margaret Cho would not necessarily mix the two and possibly harm John Kerry's run for President, and she wishes the Human Rights Campaign had believed that before disinviting her to headline their Democratic National Convention event. "It's a little frustrating," says Cho, who, it was feared, would incite scandal like Whoopi Goldberg did when she made lewd Bush jokes at a Radio City fund-raiser for Kerry. "I...