While it's true much of the West Antarctic Ice Sheet is grounded below sea level, the majority of the ice is above sea level. You can see this clearly in the BEDMAP2 dataset in this article: http://www.antarcticglaciers.org/antarctica/west-antarctic-ice-sheet

Unfortunately, it's very easy for those with an agenda to cherry-pick isolated facts and make them imply something untrue. Most people lack the science education or the critical thinking skills to evaluate the "information" they're spoon fed, especially if it's telling them something they want to hear.