None of your points rule out my first implication, and I don't believe the logic for your second point was part of Paul's statement. Despite YC companies being a small part of the world economy (or whatever), they are disproportionately mentioned on HN for obvious reasons.
1. It's relatively rare to get an angry mob
2. It's even more rare for that angry mob to target YC companies because YC companies are a small % of total companies
3. Therefore this situation is not common enough to optimize for