From what I have read, I'm not sure what anyone's complaint would be w/ what they (MM) are doing. It is simply a non-violent protest of unbelievably irresponsible, (and irresponsive), govt. non-policy.
No country, especially now, can be viable w/ open borders and no control over who migrates. That is just insanity, and it is what we have now.
If these MM people were abusing the illegal immigrants, that would be a different story. They would lose my support immediately.