It's a simple question with a really long answer. Ready for my take?
This question is likely best approached by looking at spheres of influence. For the sake of keeping my brain inside my ears, I'll keep it to big picture stuff..
It's no secret that Feminist theory depends on the blaming of men for society's ills. "Patriarchy" is a term used to denote the male sex, without actually making a blanket statement outright, but it is a blaming of all men nonetheless. There are few alive who have never heard the phrase "Oh yeah, well men have oppressed women for thousands of years, it's your turn now".
Which might be all fine and good were it true, AND you believe in visiting the sins of the father against the son. Unfortunately it's not true, and punishing one for the misdeeds of another is anathema to the legal foundations of the West.
Additionally, without the continuous blaming of men, boys may actually grow up with healthy self-esteem, men may begin to have respect in society (along with the attendant drop in negative portrayals in the media, etc).
But most importantly, without the gradually increasing demonization of men, it would be impossible to justify and gain public support for the increasing incidence of forcible transfer of power and civil rights to women, let alone force men to pay for it as well.
As the general populace goes, so do politicians. Of course, political manipulation of public opinion is nothing new, and it's a game anyone can play, in this case the only way it was possible was to HIDE it from the public, and present a false face to the public.
Without Feminism whipping up public hatred of men, Government would not be able to seize the power it has. Countless pages of legislation were written from a Feminist perspective, by Feminists, and foisted upon the public on a bed of lies. Government has used Feminism to achieve greater control over the lives of it's citizens, it just hasn't occurred to the useful idiots that it may come back to bite them in the ass...(none of them seem to believe actual, real misogyny could be manifested through an actual oppressive Patriarchal society - as evidenced from the curious Feminist tendency to support Palistinean causes and the like).
The removal of the political incentive to "punish" men for "irresponsibility" (especially in cases where women are not held to the same standard) will quite naturally lead to more egalitarian laws/services.
The removal of Feminism would not eliminate Affirmative Action. What it would do, however, is allow men to push for jobs in Healthcare, and Education, and other female dominated industries.
It would smooth relations among staff members, and maybe people would be OK with socializing with co workers again (without fear of a "sexual harrassment" suit), removing the power of a control-freak few who believe they should be able to dictate the behaviour and even thoughts of others.
It would also diminish greatly the male bashing and sexist jokes rampant in the workplace today, ironically enough.
Workplace deaths would not be affected in and of themselves, but the removal of impediment to actually admitting it is men dying might speed improvements.
Every single country in the West has the same problem... Disaffected boys faring terribly in education at all grade levels. Decreasing enrollment, higher truancy, lower grades...
ALL of that would disappear damn near overnight with the abolishment of Feminist thinking from schools. This is not a surprise to anyone, although dyed in the wool Feminists will still deny, deny, deny. But when your local School Board "studies" the problem, and the report opens with Preamble expressing support for Feminist principles (now why would THAT be necessary when speaking of BOYS education I wonder?), and then goes on to blame the socialization of boys as culprit, and recommends "awareness campaigns" and programs to CHANGE THE BOYS, not the education system, well....denial gets a little harder now doesn't it? When they suggest spending $40,000 (yup, 40 Grand) on non-fiction books for school libraries is a significant improvement, it kind of seals the deal.
Coupled with AA practices to fill teaching positions with men until they reach proportionate amounts of teaching positions, and the freedom to teach reality, rather than dogma, Western education systems will improve by leaps and bounds...especially once you consider the resources freed up when parents are once again allowed to provide moral guidance for their children without competition from the schools.
Perhaps most importantly, massive numbers of little boys who have irresponsible mothers (aka Single Mothers) will at least get SOME male role models that aren't bad boys that fuck Mom real good.
Men die earlier than women, everyone knows this. What many don't know is that at the turn of the century men and women lived roughly the same length of time. The removal of Feminist Dogma from the public discourse would allow increased attention to Men's Health. Opposition to Men's Health Commissions would vaporize, misinformation about medical spending (both research and practical) would stop, and the public could see just how unfair the current situation is, and call for change (or at least volunteer some time to male specific causes).
Public support for such things as entire hospitals being reserved for women, or "screening programs" not mirrored for an equivalent problem for the other sex would be lessened.
Men would live longer, healthier lives.
The treatment of men from all sides is abominable when it comes to man vs woman cases. Removal of Feminist jurisprudence would be quite likely the single largest benefit to men to be realized, should it come to pass.
No longer would men be thrown out of their homes on nothing more than the word of another.
No longer could the Government strip him of his possessions, children, and basic civil rights.
No longer could a man be incarcerated, slapped with a felony on their record, be condemned to a life of poverty, lose their livelihood via removal of licenses, and spend YEARS in Prison without criminal conviction - simply because they slept with the wrong woman and don't make much money.
No longer could men be forced into Parental responsibility unwillingly, no longer would men's children be given to others with impunity, no longer would men have ZERO right to custody of their child, unless married to the mother.
No longer would men have their lives ruined, their name dragged through the mud in the media, their bank accounts depleted, their relationships strained or shredded...all on the word of one woman. And no longer could that woman enjoy immunity from prosecution for such wrongdoing.
No longer would prejudice against men be so encouraged that men routinely recieve harsher sentences, and more frequent convictions, than women.
Perhaps most important of all, men would no longer be blamed for all of these problems.
Sure, there's a lot more to be said. I missed a LOT of stuff, but I think I've made it fairly clear that Feminism is a harmful force on society in general, and men in particular - elsewise why so much benefit to men in it's absence?
It's a good reason to keep the eyes on the prize. Because all that, and much much more, could very easily happen. If we work hard enough.