Well - IMO Insurance companies tend to spend a lot of money figuring out the odds of an accident and price their insurance accordingly.
So unless you have reason to believe you're particularly accident-prone on a motorcycle, it's probably a losing bet.
The case where insurance makes sense if you're protecting yourself against a potential cost that would be life-changing (in a bad way).
If you can afford to pay the deductible without having it have a significant impact on your finances, it makes more sense to self-insure.
Sure, this coverage seems like a small amount, but throughout your life your going to be faced with a lot of choices like this (damage waiver on rentals, travel insurance, extended warranties, etc.) - just follow this philosophy with all of your choices, and on the whole, it should add up to enough savings that you come out significantly ahead (unless you get really unlucky, of course).