This is an assumption made: that defecation and urination are technical terms. They are not, any more than penis and vagina are technical terms.
Is one only willing to accept crass or childish terms for everyday events, like breathing and eating? Do we adults pee and poop?
If you can't say defecate with a straight face, one can refer to passing stool, gas, or water. Or have a bowel movement, pass urine, pass gas, or relieve oneself. To make such universal functions taboo is to cave to Victorian fantasy that these things are simply never recognized.
Learning to exert control over our bowels and bladder is one of our first socializations in childhood. We are taught that passing stool into our underwear is socially unacceptable. But the vast majority of us are successful in mastering this skill, and we are proud of it when we do. Maybe Freud is to blame for making passing stool a traumatic experience.