contentious, moot, disputable, arguable, polemical, debatable, polemic, controversal, provocative, unpopular, more...

unanimous, agreeable, accepted, uncontroversial, harmonious

global warming, stem cell research, death penalty, gun control, gay marriage, immigration, affirmative action, more...

not agreed upon,   hot button issue,   divisive topic,   much discussed,   hotly debated,   often discussed,   causing a stir,   politically charged,   under debate,   often talked about