Data vs Code
There is a good reason why Bitcoin doesn't use Smart Contracts. It's simply to not have code in the blockchain. So all you have on Bitcoin is data. Sure that data may break some really badly written software that works on it, but then you need to fix that software. Essentially you can do that by having a problem that checks the data to conform to the syntax you are looking for and ignores messages it cannot proof to be correct. After all, Parsing is a well established science.
However with Smart Contracts you have Turning complete code in your blockchain, which is, in principle, impossible to proof correct.
Biting the hand that feeds IT
