"If the Mexican government has already slowed down the flow by telling illegals not to cross, couldn't they ALSO conceivably have told them to scream about their 'bad' treatment at the hands of the Minutemen?" So you are saying the Mexican government could have been doing this all along, that is to discourage any illegal crossings? Did they print any pamplets on that subject?
Not sure about pamphlets, but here is one about fliers from 'Mexican migrant-aid groups':
Minutemen aside, some migrants undeterred
And here's one about the Mexican police:
Minutemen find few migrants (Police in Mexico discouraging illegal crossings)
Just do a FR search for Minutemen...it brings up lots of info.