It's the subjective part I don't like.
Ask it another way ... what's the difference between your automated trading platform placing buy orders then cancelling them and placing sell orders because it was trying to manipulate the price, and your automated trading platform placing buy orders then cancelling them and placing sell orders because it got new information and decided to trade the other side of the market ... 200 times in one day.
I suppose at least in that case you have code and a record to prove that the algorithm did it for all the "right reasons".
I wonder about the wisdom of trying to protect one set of traders from another set of traders, none of them is really providing any value added to anything in the market except that they add liquidity.
That's not really it at all. Spoofing is pretty easy for the CME market compliance group to track and monitor and it's not nearly as subjective as you suggest. CME has brought at least a dozen cases that I've seen against both independents (individuals) and big trading firms. All electronic trading exchanges monitor the message-to-fill ratios of each tagged participant - they've been doing it since the early 2000's. The order book bias, extreme sizing changes, and cancel/replace frequency for a spoofer leaves a totally different electronic footprint than your typical automated trading platform or algo.