Mark Zuckerberg gave an impassioned opening speech at Facebook's F8 developer conference keynote today, lambasting Republican presidential candidate Donald Trump and his supporters for cultivating a culture of fear in the US. Though he did not name Trump directly, Zuckerberg referenced the candidate's position on immigration and the infamous call to build a wall between the US and Mexico. The Facebook CEO says fighting against this mentality is an integral part of his company's 10-year roadmap.