When I took Exegesis in seminary the teacher talked about this passage. Some factors we should remember that are different from our culture to the one in which Paul was speaking.
1. There were those who were eunuchs in the ancient cultures. As such, there was those who performed castration on themselves. There were those who were made eunuchs as babies. While this seems a remote and almost mythical practice to us, thinking of the harem guards of story books, it would not have been absurd in Paul’s day to have met a eunuch. I don’t believe I have ever met a eunuch, so that puts this category of thinking outside my normal system of thought.
2. Leviticus 21:20 forbids Aaron’s offspring to serve as a priest if he has injured testicles.
3. In Roman religions there were temples that had castrated priests.
There is a distinction between the Jewish practice of circumcision and the Roman religions that practiced castration of the priests. Paul’s statement is probably sarcastic but not in the way we would take it in our culture today.
Speaking to Aaron’s sons, Moses addresses the idea of being cut off from the presence of the Lord for uncleanness in Leviticus 22:3–
3Say to them, ‘If any one of all your offspring throughout your generations approaches the holy things that the people of Israel dedicate to the LORD, while he has an uncleanness, that person shall be cut off from my presence: I am the LORD.
The whole idea of cleanness or uncleanness is associated with the concept of circumcision. The question comes to mind, if these people who were advocating circumcision as a means of achieving cleanness and right standing before God, what if they had gone too far in their practice of circumcision and instead of in the act of circumcising themselves they actually injure themselves, then they are permanently in the unclean category (See Lev. 21:20). They then have to start to think about what really makes one clean or unclean, and of course they have to start thinking about faith alone. Which of course where Paul is going with this. I would take Paul’s statement of hyperbole, but with an actual point. What if someone does not a pristine body, what if he is not without blemish? Can he be saved? The answer is yes he can be saved, and it would be better to have some blemish that made him depend on grace rather than have the perfection of organs and depend on the flesh to save him.