Lebanese security forces used excessive force, including firing live ammunition, against anti-government protesters after the Beirut port explosion, Human Rights Watch (HRW) said on Wednesday.It called for an investigation into the abuses.The Aug. 4 detonation of highly explosive material stored unsafely for years killed at least 180 people, injured about 6,000 and damaged swathes of the city, and fueled outrage at a political class already blamed for an economic meltdown.