The issue is that not everyone have the same standards of hygiene. I even know a mum who believes that good hygiene is more important than good grades! There is no right or wrong. Yes, ideally, you want your kids to wash and be clean, but for some it will be low in their priorities, and that doesn't make it right or wrong.
The problem is when a SM is trying to impose her priorities and that can have some real bad consequences. As an -clean- adult, I can look back and see that I had poor hygiene as a young teenager. Why? Because my self-esteem was in tatters. I was body conscious, so hated getting naked. I also absolutely hated being cold and at the time, we just had a small radiator that took forever to heat. It would sound ridiculous to most adults, but I also hated water (now can't get me out of it!), so taking a shower was a big deal for me. My parents tried to get me to do so more often than I did, but didn't label me by my poor standards, instead focused on what they felt was more important. My SM though seemed to me obsessed with it and I felt that it defined all she cared about in relation to me. As a result, it made me feel extremely anxious and the more she made comments, the more self-conscious I became.
Thankfully, I moved with my grand-mother when I was 15 in a new town and for the first time, I started to believe that I wasn't ugly. This made me gain confidence and with it, I started to pay more attention to my appearance. Before I knew it, I took a liking in a boy and my grand-mother couldn't get me out of the bath.
My DD hygiene was not too good around 11 or 12, but then all in a sudden, she was in the shower every day without me reminding her. DS is not great either (despite demanding his bath time when he was younger), and I do have to remind him about showering and brushing his teeth, but I am confident that he too will get on with it when the time is right.
Stressing a teenager about hygiene is the best way to alienate them and make them want to withdraw. However unpleasant it is to be around a smelly teenager, it is not half as bad as a teenager who decides he dislikes you much.