Bleeding gums are a bad symptom is what you're agreeing on. You're saying "That should never happen". He's saying "That's nice, but frequently when I switch t

Bleeding gums are a bad symptom is what you're agreeing on. You're saying "That should never happen". He's saying "That's nice, but frequently when I switch to a new toothbrush it happens". Meaning that his old one was no longer cleaning his gums properly. Hence his original proposition that one needs to change toothbrushes more every few months.