Masturbating is an illness?

Just now I was asking my mother if she thinks my brother knows how to masturbate because at his age, I thought it'd be odd if he didn't know how to or if he didn't even feel the need to. (I got this idea because a lot of the guys around me are like that at my brother's age.)

My mother replied,
Huh? Masturbating is a disease, an illness lehz!

I am really quite shocked. I never knew there are people who thought in this manner, much more in the form of my mother.
If that's what she thinks, then is my opinion that masturbation is perfectly fine, wrong? Am I thwarted? Confused.