Are our Slants "Unsafe"?

so riding in a car without a seat belt is still several thousand times safer then when I am on my bike

Yes, in exactly the same way as playing Russian Roulette with 2 rounds in the chamber is safer than playing Russian Roulette with 6 rounds in the chamber.

seat belts are good and I use them when I feel it is appropriate, perhaps 50% of the time

I'll pay ya two hunnerd dollars to park your car for a day so I can use your crystal ball. It sounds like a good one, able to forecast which car trip isn't going to be the one in which all the sudden you get hit. (I'm being sarcastic; the point is your "feeling" of when it's "appropriate" to wear a seat belt has zero relation to your actual risk of being hit. Believing otherwise is about as logical as believing in the tooth fairy or the Easter bunny, but the consequences are far greater.)