I get this completely but it defeats the purpose of a good survey. Skeptic is so vague that it creates a bigger problem.
Okay. You have a category in mind that you wish to study. Conventionally, you believe the word for this category is "atheist". Now we've established that this word is emotionally loaded and using a survey to find people who self-identify with this label is not going to match the category you have in mind. You've decided to move on to skeptic. This word is not emotionally loaded but few people self-identify with this label. Maybe you can suggest a better methodology to identify people in the category you wish to study?