Sweet Potatoes are pretty high in carbs but the sweet potatoes are not bad carbs.
As long as you eat the sweet potatoes in moderation then the carbs in sweet potatoes are not bad.
However if you eat too many sweet potatoes then the high carbs in sweet potatoes could be bad for your health.
Sweet potatoes are full of nutrients, vitamins, minerals and fiber which all healthy for you in moderation but just like anything that is healthy it can be bad when consumed in excess.
Sweet potatoes are low in calories though which makes them a good food for eating when you're on a weight loss diet.
I've eaten sweet potatoes while on a weight loss diet and ate other foods such as salads, regular potatoes etc and lost 100 lbs of weight in a years time.
I did of course also exercise which is needed to really lose weight.