There's nothing in the article saying that it's "worthless" if it's dirty, it would be "worth less." Less than the possible original value, not wholly no value. Readers here should be aware of that fact first.
I don't think it would be entirely applicable for apply the type of standard such as LBMA because all of the Bitcoin in the network are from the system itself, and you could never add to the supply that it has now. According to the wiki, the function of LBMA is quoted below.
LBMA's mission “is to add value to the global precious metals industry, by setting standards and developing market services, thereby ensuring the highest levels of integrity, transparency and trust.”
There are factors like making Bitcoin more precious would be the ideal purpose of the "future standard" that's going to be applied to Bitcoin, but technically, it's going to take a lot of hard work, IMO. It doesn't make sense anymore, as long as you have Bitcoin in your wallet, you are good. If you are transparent where you got it from, it would be good. I don't think it's worth discussing.
It's the people who are Dirty, not Bitcoin.