The main damage is indeed caused by tar (I hope this word is translated correctly), as it harms mostly your lungs. From what I have heard from my surroundings, I would also think that nicotine itself is pretty much harmless, but it is probably just in the shadow of the harmful smoke.

I have respect for drugs. I would say I consume a lot of caffeine (technically, it is also a drug), but on the other hand, I do not have a big problem with avoiding caffeine. I do not have any experiences with forbidden drugs. Occasionally, I drink a few glasses of alcohol - just the amount the society demands :D. But that is all.