Summary from Wikipedia

Despite being a member of the Communist Party of Yugoslavia, Popović was a supporter of free-market reforms[1] and was also a member of a group of Serbian liberals, a prominent political movement in the 1970s, which also included Marko Nikezić and Latinka Perović. He retired in 1972, amidst pressure against his group of liberals. He spent the rest of his life in Dubrovnik and was very outspoken against the Yugoslav Wars and the regimes of Franjo Tuđman and Slobodan Milošević.