Yes, keeping your testicles cool is critical for keeping them healthy, but this does not mean that icing them is a good idea. The point is simple:
You don't want to over-heat your testicles.
But, you also don't want to over-cool your testicles.
Over-testicular hypothermia is associated with a whole set of negative symptoms as well. So--normalizing testicular temperature is key.
On the other hand, short-duration (10-30 second) cooling treatments are actually beneficial, especially to overcome heat-stress. This is because the modern lifestyle is heat-toxifying, and also that cooling has inflammatory effects, and also promotes healthy vascular function.