In reality, and I quote:
A rep from Facebook said the cushion was not the billionaire’s private seat, but was provided by the Senate Judiciary Committee. “That’s the committee’s standard practice,” a company spokesperson told The Post.As you can see, people simply projected their own feelings about height onto Zuckerberg. However you may feel about the guy, to automatically assume he's insecure about his height is nothing more than conjecture, founded on the basis that male shortness is something that must cause embarrassment.
This doesn't only happen to short men who draw the public's ire, but to short men in general. Here it is happening to Kit Harington. People will automatically assume you're insecure just by existing.