Why is it bad, exactly?
It's bad because it reduces the demand for spot Bitcoin. Pretty self explanatory, right?
No. How does the CME market do that?
CME (or Bitmex) can't be used to push prices around so it doesn't matter how many shorts or longs pile on. There is no mechanism to make the spot markets follow them; they won't. However, large traders can take positions on CME or Bitmex and then pump/dump on spot exchanges, and I'm sure that's exactly what is happening.
There have been plenty of instances where bots do replicate the movements of CME and Bitmex. Perhaps not to the exact dollar, but close enough is close enough.
I've never seen
any examples of that, let alone proof that there is a statistical correlation. Logically it just doesn't make sense since there is no arbitrage pressure to drive prices towards CME or Bitmex prices. There
is arbitrage pressure to drive CME and Bitmex prices towards spot, since their index/reference rate is based on constituent spot exchange prices.
In other words, CME traders very much care what spot exchanges say the price is. The spot markets have absolutely no reason to care what CME does though. Volume doesn't matter in this respect because no BTC is being traded on CME.
It makes sense as well because those trading at CME are most likely institutional players (which is where most of the demand came from this year), and the volumes are well above that what spot exchanges generate.
That supports the theory that institutions take positions on CME and then push spot exchanges on low volume. That makes a lot more sense than bots on spot exchanges following CME.