As the OP mentioned, all teenagers don't get into wrecks, and many non-teens get into accidents all the time. But teenagers cost more to insure because they have a higher likelihood of getting into an accident than non-teenagers, which means that they cost the system more. Either you charge teenagers more, because they cost more... or you charge EVERYONE more, because TEENAGERS cost more.

You're taking a very strange position here. You're saying that when an individual makes a personal choice (being fat, or smoking), he/she should not be asked to pay for that cost individually - but it should instead be socialized and distributed to those who did not make that same costly choice...

That is an EXTREMELY odd stance for you to take.

No-one is saying "you can't be fat". We are saying "Being fat carries a much higher cost, and if you make the decision to be fat we do not want to carry that cost for you, so we will ask you to pay in a little more to cover that extra cost."

There are only two other options:

One would be to say "Well you made a decision to be fat, now you cannot have any insurance."

The other would be to say "We're sorry that you made a choice to be fat, now we'll all have to increase ALL OF OUR costs to accomodate your higher health care costs."

I wouldn't have been surprised had you taken the "no insurance for fatty" option, but I'm SHOCKED that you just want to let fat people be fat and socialize all the additional costs that result from their choices.