There can be parallels between people who believe that overpopulation is or will shortly be an issue of major concern and fascist dictatorships. They aren't necessarily compatible or incompatible, depends on specifics. Some people think that education is enough to help prevent/lessen the effects of overpopulation while others feel it's the duty of the State to step in. Whether or not you are "facist" about it depends on what perspective you're seeing this issue from.
I see it from a libertarian perspective, so I don't think government should be too involved in it. Obviously China has been successful at keeping their population down with forced abortions, and at least they're fair about it, but I don't think that's the "right" way to do it. I don't think you can deny that overpopulation is a currently a problem if you look at the most important stats(population, food production/distribution, quality of life, etc).
I knew a guy once who took the Earths total land area and divided it by the population(which was a little more than 6 billion at the time) to "prove" that every individual on the planet, if land were evenly divided, would own about 1 square mile and, therefore, overpopulation is nonexistent.
I don't think he took into account vital ecosystems which are necessary for the health of the planet. I think he also forgot about how much land is desert, frozen solid or otherwise unsuitable to sustain human life. If he had taken into consideration how much arable land we have, he would've come up with a number closer to 7 square yards....which isn't even room for a small house.... Obviously that only works if everyone becomes subsistence farmers but you probably catch my drift.
Either way, overpopulation is a problem or misappropriation of land and other resources is. We could over simplify it and present it as an ultimatum - Facism or Socialism, or we could start using a greater percentage of our wealth on developing extraterrestrial living environments. Considering how incompatible the social systems of the 19th century are with our present state of existence we would be regressing if we continue attempting to apply them. Yet another option is to deny that an increasing population is detrimental to the planet and it's inhabitants and continue living like you are now. There is definitely a chance that overpopulation won't personally affect you in your lifetime. I think the best option, even if you deny that overpopulation is an issue(consider it gift to your 40 great-grandchildren) is to get(as many people as possible) off of this planet and on to the next one asap.