The question becomes Morangias is your definition of normal the norm? Is your definition of it accurate? The truth of the matter is we cannot be sure because the point is left vague and even many of our examples suffer from sample bias, their taken from legendary historical records or sample bias. I mean the Grey Knights keep coming up in discussion, the Grey Knights arn't even normal by space marine standards as their effectively mentally created by the inquisition to be perfect little anti-demon soldiers. I would think the implications of the Grey Knights would be horrifying to even the stauchest pro-imperial space marine chapter not an ideal to aspire to.
I think for me it comes back to this: If space marines were incapable of having sex or fathering children they would have said so explicitly. Since they didn't I must assume that they can, that doesn't mean that all of them want to or even have an interest but it leaves a whole host of possibilities, and ultimately since good stories about space marines or anyone else pull back to their conflicts not just martial but about their nature I think the writers have likely intentionally left that tool in the toolbox. Likewise I think that to believe that sexual urges are a detriment to the quality of soldiers sells the mental qualities of those soldier short. In short I believe that the emperor whould be more concerned with soldier who would live the monastic ideal because they believed in the monastic ideal rather then because they were forced to. Further by my understandign the emperor himself didn't live the monastic ideal as there's hints that he had kids, and lots of them.
TLDR: It's not any more mature to have celebate space marines then not, it's not any more effective to have celebate space marines then not. What i think is important is how you handle the stories of each.



