I discussed this topic recently with some people who stutter and some who don't. The bottom line that came out was "Everyone is afraid of being judged." Public speaking puts you in the spotlight and "invites" judgment, in a sense. For PWS, the obvious and immediate "problem" is stuttering. For non-stuttering people, the trigger may be more vague or ill-defined: "I might do X which will make me look bad," even if you're not sure what X could be. Ultimately, everyone needs the same mindset...who cares what other people think! Do your thing and be you.