It feels like the author is confusing cancer with sperm count. So he spends half the article discussing how cell phone signals don't have the energy to cause DNA breakage and then cause cancer. But this is about sperm count. All you have to do to lower sperm count is increase the temperature. It's been shown that just bathing the balls in a bowl of hot water daily drastically reduces sperm count. So heat is definitely contrary to sperm production, and it isn't as tough to produce as DNA breakage. That said, there is no permanent damage. Sperm production resumes when the temperature returns to normal (which is below body temperature for the balls hanging out of the body).