I'm mainly going to use the body count topic as a point of reference, but to put it like this, people seem to have the idea that if you don't date a woman who has a high body count, it's automatically based in insecurity and it can't be anything else.

This is obviously wrong, and it's an argument people who can't critically think use, it's very black and white. Now insecurity CAN be a factor. This would be an example of insecurity:

"I don't date women with high body counts and neither should you. If you disagree with me you're just a weak bitch."

Now that's insecurity, because you're trying to place prescriptions onto other people, and you're trying to say your world view is the correct one, and that everyone needs to fall in line. Saying you won't date a high n count girl so that means everyone else should do the same IS insecurity.

Now let's talk about what most people say when they talk about this preference:

"I personally wouldn't date a high body count girl but I understand that others don't feel this way which is fine, we're all allowed to have our personal preferences and standards."

THAT'S not insecurity, because you're not trying to force people into your world view, you have your preferences and know others have theirs, you aren't telling them they're wrong and as long as they're happy that's fine.

TLDR: Insecurity comes down to whether or not you place a prescription of your world view onto others or not.