Clearly, it's stating the obvious to say that at one level a 'passable' grammar is essential to being understood. Flout the rules entirely and you are speaking gibberish, or being poetic. The brain has a remarkable ability to look for sense in the seemingly meaningless. Random word collisions can evoke powerful images. Though perhaps ironically that's because of the grammar rules too. I don't think that's the point being made by the OP though. I doubt Andy Murray was being poetic.
There are different grammars for different occasions. If you want that job then you might not speak to the person interviewing you in the same manner as you'd speak to your friends. Or you might speak to a policeman differently to how you might speak to your lover - perhaps

.
It is perhaps less a matter of bad grammar as inappropriate grammar. It might be beneficial in some contexts to choose appropriately. Not a good thing or bad thing, more of a thing thing.