BERLIN, Aug 17 (Reuters) - Pictures of masses of people trying to flee Kabul are shameful for Western nations, German President Frank-Walter Steinmeier said on Tuesday after photos showed throngs of desperate people at the airport after the Taliban seized the capital. "We are experiencing a human tragedy for which we share responsibility," said Steinmeier, who holds a largely ceremonial post, adding that everything must be done to help people threatened with violence in Afghanistan.