Well luckily I am not easily offended - but if I was to take some opinions to heart I would have to give up my teaching career now.
I have never danced professionally it was never something I wanted to do - there are too many good dancers out there who really want to dance professionally without having someone who only wants to teach struggling to find a way in so that they can gain "experience".
I only ever wanted to teach. Why? because from a fairly young age I realised I was good at it. I could relate well to students of all ages and found that I could make a difference, help them improve and reach their potential. I am not the best teacher in the world but I do not claim to know everything and i am always striving to improve myself as a teacher and do not rest on my laurels.
Anyone who teaches dance to all - i.e to students who are coming to primarily take dance as a hobby can't honestly say they could get a talented dancer to professional standard on their own. At some point they would need to let this student progress to full time study and before suggest they take their dance further i.e by auditioning for an associate programme perhaps. But what all teachers can do at a local level is ensure that all their students receive a solid grounding and achieve their own individual potential.
I have studied for years to become a good teacher, both in dance but also other related areas such as teaching methodology, effective lesson planning, class safety etc. I think that although I have never danced professionally I have become a good teacher through a combination of natural ability and through a desire to do my job better and better all the time.
There will be good and bad teachers, some of those will be ex professional dancers and some won't. I think it is quite an unfounded generalisation to say that only one category will make good teachers. I think most of us know of examples of good and bad in both category.
Teaching goes far beyond such a superficial level. What makes a good teacher is not as easy as just looking at someone's cv. It is one job where really the proof of the pudding is in the eating.