At a time when U2 prattling and droning about Martin Luther King dying with love in his heart (and a song on his lips, I imagine) is thought to be political art, the left desperately needs an art and a politics that are more clear-cut and specific than ever, an art and a politics that spell out exactly who and what it's fighting for. This benefit for medical aid to West Bank and Gaza Strip Palestinians is getting there. Headliner Gil Scott-Heron has spent 20 years making the best kind of pissed-off pop art; his music ranges from loose-jazz personal meditations on deprivation to cold, methodical exposes on power rapped-out over smooth, killer funk. An experienced, sharp performer, his attacks on racism, imperialism, and the right-wing renaissance have always struck home, but in this setting, I expect they will gain even more precision. Though I haven't heard the other acts--a Palestinian folk troupe, Al Waton, is in the lineup, and so are the Sechaba Singers, an African National Congress-sponsored South African vocal group--together they form a cross-cultural support group that will widen and strengthen the message of informed resistance. Tonight, 8 PM, Medinah Shrine Temple, 600 N. Wabash; 266-5000.