taken from Bear's site

Myth - "Underwear supports the testes and keeps them from getting floppy."
Like the bra is said to prevent the sagging of breasts, underwear is supposed to give support to the testes. Imagine putting your arm in a sling and not using it. Will it become stronger? Healthier? No, it will become weak and atrophied. 'Going Bear' is healthy!
Myth - "Cold is bad for the genitalia."
Doctors specializing in reproduction therapies state coldness on the testes is not harmful. In fact, it increases sperm motility. Ice on the testes is a common recommendation for men with low sperm production.