Celibacy is a choice, but chosen for the wrong reasons and it never works. Need I point out Ted Haggard, Larry Craig, George Alan Rekers, Eddie Long and similar gay men who were celibate from gay sex due to cultural/religious reasons. These men convinced themselves they were straight and they lived their lives in such a way they were anti-gay in everything. Eventually though "will power" gives up and they gave into their instinct, even though giving into their instinct lead to so much self destruction in their circumstances.

Celibacy is a choice, and sometimes it works, but it can not work for everyone, and it will never work if the reasons are wrong. Not having kids for it would make the world more just, or people will suffer less is not how our reptile brains work. People are going to have sex.

If you want less kids, then you need greater access to birth control, better education on birth control, and less stigma associated with it in certain areas of the population.