A reasonable question.
First, though, understand that male circumcision is not thought 'perfectly fine' by everyone. Indeed there is a small, but growing, worlwide movement to ban the practice (or at least ban doing it to kids before their age of majority.)
Still, today, it is not viewed in a harsh negative way. Look at the differences between the two customs:
1. Male circumcision (MC) does not result in a lifetime of pain during sex, as FGM does, in many cases.
2. MC does not prevent men from experiencing orgasm, as FGM typicall does, and is designed to do. The goal of MC is not the fundamental alteration of a basic function of the human body.
3. MC is typcially done to infants, who are not angry and traumitized by the experience (or at least not able to remember being angry and traumitized as adults). In contrast FGM is done at age 12, against the consent of girls who well remember the force and coercion used on them.
4. MC rarely results in death or serious complications. FGM has much more frequent complications.
5. MC may have some health benefits, particularly in cultures where frequent bathing is either not possible or not practiced.
6. MC is a Western tradtion, thus people in the West consider it normal Few people in the Magrib consider FGM a terrible practice, it is normal there.
Well I was so traumatized when I was cut that I couldn’t walk for a year.