I agree that you are responsible for your own behaviour. The reason I believe this is because you make your own choices. Your behaviour is determined be how you react to a situation. Every body has the ability to decide there own fate and chose how they react. Genes play an extremely small role in our overall behaviour.
I did nothing -- could have done nothing -- to cause my thyroid cancer. Many of my immediate family have died of cancer, including brothers who died of a brain tumor, leukemia, stomach cancer and lymphoma. My dad had kidney cancer. Only one died of lung cancer, a smoker, which I feel was her own bad behavior.
While it is true that certain cancers are tied to certain behaviours, it is also known that there exist individuals that do these behaviours and don't suffer from cancer. It's more likely that our genes make us either weak or strong against events that trigger cancerous mutations in our bodies
There is ample evidence to prove that cancer is caused by things that we do, such as smoking, tanning, and abusing alcohol. However, there are a lot of cases of cancer where nothing in particular appears to cause it. It is thought to be genetic in some cases, and there is nothing to blame but our bad genes in such instances.