This is true. Serbs did commit ethnic cleansing and atrocities across Bosnia and Croatia. Please see https://en.wikipedia.org/wiki/Ethnic_cleansing_in_the_Bosnia....

Ethnic cleansing occurred during the Bosnian War (1992–95) as large numbers of Bosnian Muslims (Bosniaks) and Bosnian Croats were forced to flee their homes or were expelled by the Army of Republika Srpska and Serb paramilitaries.[6][7][8][9] Bosniaks and Bosnian Serbs had also been forced to flee or were expelled by Bosnian Croat forces, though on a restricted scale and in lesser numbers. The UN Security Council Final Report (1994) states while Bosniaks also engaged in "grave breaches of the Geneva Conventions and other violations of international humanitarian law", they "have not engaged in "systematic ethnic cleansing"".[10] According to the report, "there is no factual basis for arguing that there is a 'moral equivalence' between the warring factions".[10]