Former President Barack Obama slammed GOP nominee Donald Trump's "weird obsession with crowd sizes" during his speech at the Democratic National Convention on Tuesday.Andrew Harnik via Getty ImagesGOP nominee Donald Trump loomed large in Barack Obama's speech at the DNC on Tuesday.Obama slammed Trump's "weird obsession with crowd sizes" while making a suggestive hand gesture.Obama said Trump has "not stopped whining about his problems since he rode down his golden escalator nine years ago."Former President Barack Obama tore into GOP nominee Donald Trump during his speech at the Democratic National Convention on Tuesday.Obama took multiple swipes at Trump during his address, calling him a "78-year-old billionaire who has not stopped whining about his problems since he rode down his golden escalator nine years ago."And while Obama is known for his oratory brilliance, it was the combination of his rhetoric and a suggestive hand gesture that made one of those jabs go viral."It has been a constant stream of gripes and grievances that's actually been getting worse now that he's afraid of losing to Kamala," Obama said about Trump."There's the childish nicknames.