That is always concerning, additionally a difficult question to answer. It seems natural to personify an AI however what would it want? The creation of a language (is it similar to babies babel) to the development of a conscious thinking entity are completely different, and to suggest it would 'want' to cause any devestation would be questionable.

Shutting it down could be as simple as deleting the program off the block chain, to suggest a rouge AI could be developed at humanities level of technology at this stage seems a stretch in ones imagination. In saying this maybe there should always be a failsafe System.exit(0) in all AI software incase of it going rouge or developing a level of intuition comparable to humans. I would suggest questions like, "Ethically should we even shutdown any AI that has started to develop its own language?" Would be more impertinent to answer.