On the other hand: One hangs lower than the other to prevent
crushing; the skin forming the
scrotal sac can actually
thicken to
protect them (and does during
coitus in order to keep them from jostling each other); they can be
retracted back into the body using either
voluntary or
involuntary muscle; and if you have a big enough
Johnson, a kick to the
groin may be harmlessly absorbed by said
Johnson, which does not have many
pain receptors. It's also hard to kick someone in the nuts from behind, since the
thighs get in the way, although if you just stick your foot far enough forward your
shin will do the job.
Even so... The human brain is aided by extra blood vessels which help regulate internal temperature. The doodads could easily be located in a more protected area, and kept cool if there were enough blood vessels to regulate the heat.