If you floss too hard or aggressively then that can be bad for your teeth/gums. If you floss only rarely causing your gums to bleed when you do and you don't wa

If you floss too hard or aggressively then that can be bad for your teeth/gums. If you floss only rarely causing your gums to bleed when you do and you don't wash or brush away the dried blood, that can also be bad. But I don't believe that any dentist in good faith would advise not to floss, if done properly.