As you said, sportsbikes can be dangerous, and it does depend on the rider. If you go and purchase an R1, and go and ride like a maniac, for sure you're going to hurt yourself
However, with the right education and self discipline riding can be very safe and rewarding. What have you got on your side? Well a sportsbike has a very small frontal area (can fit into small gaps!), awesome acceleration (good for getting out of tight spots), excellent brakes (if you know how to use them to their maximum), and they are very agile. You'd think from that that you'd be one of the safest vehicles on the road.
However, you have only two wheels, and you're anything but travelling in a straight line and one of these stops spinning, you're probably going to have a "get off".
Newbie riders often perceive that riding a motorbike is all about physical motor skills. Actually this is only a small portion of what it takes to be a safe rider. A car has a cage, you have your brain. This is your primary defense against an accident. It's about knowing what your bike is doing and why, AND being able to spot a potential accident before it occurs.
An example of this: your riding down a sidestreet coming up to a slow moving car. At this point alarm bells should be ringing in your head. A prudent riding will be asking "why is this car going so slow?". A squid will just get annoyed, open the throttle and attempt to overtake the slowcoach infront of him/her. At the point at which the bike is too close to the car to stop, the car will then pull a u'ee without indicating, and the rider will slam straight into the car.
I had an accident very similar to this a couple of years ago. Only problem was that it was a bit harder to spot than the above accident. The car had just pulled out of a gas station and was accelating slowly. I came up in the other lane, and at the last minute, bang, this car pulls directly infront of me (doing a u'ee). No way I could have stopped. I was lucky to get away with only a broken arm considering I hit the car in the drivers side door (ie in the cage). Lesson learned: RIDE DEFENSIVELY
. It does not matter whose fault the accident was - I still got hurt.
I've gone on a bit, but I think you get my point(s). Never stop learning, always leave yourself an out, and ride defensively. It may never be as safe as driving a cage, but you only live once right?