This guy is really missing the point. Fixed costs aren't just overhead - they're fixed. Even if you decided to stop selling, you'll likely still be paying them

This guy is really missing the point. Fixed costs aren't just overhead - they're fixed. Even if you decided to stop selling, you'll likely still be paying them (e.g. a lease on a building). If times are tough, it still makes sense to sell below cost but above variable cost to reduce the sting of the fixed costs. If you want more details, read a micro 101 textbook.