What does multiculturalism have to do with anything? Multiculturalism is about acknowledging, accommodating, celebrating, and even drawing strength from the diversity of those who live here, no matter their heritage.
Immigration is about who gets to come here and how many. If we're actually letting too many in, then that is something to deal with, but it's completely separate from whether we celebrate what we have to offer each other.
I have always been suspicious of any "rights" movement among those with power. Whether it's "White rights," the "rights" of corporations, the rights of the property class and wealthy, or Men's Rights. It is not that such rights do not exist or that there are no grievances deserving of redress, it's that they too often are self-serving attempts to retain or increase power.
I am of the opinion that the vast majority of legitimate male grievance against society would be better addressed by bringing to heel the corporations, the wealthy, and those who seek political power for personal gain.