What agenda are they pushing exactly?

In essence all MGTOW are in polyamourous relationships by default because we have no interest in committing to one woman and open to have sex with many (if that's what we want)

calling open relationships "marriage" is redundant, you are DATING, that's what I do when I DATE women

or does it make it a true polyamourous relationship when the woman has the option to take half your shit...