Ive had a vagina my whole life. Doesnt make me a gynecologist
I think the advice to take courses in training, first aid, emergency protocols etc., is very sound. I believe BoredomBusters offers courses on setting up a dog walking business. You may want to check her out.
I walk a great dane and an 80 pound mutt dog daily, and never consider their combined weight. I walk horses all the time and again, dont consider their weight. Control is not about being able to physically overpower a dog, its about your ability to communicate with the dog in a way they will understand and cooperate. Obviously this isnt going to happen until you have a relationship established with that dog, which is why if I were a dog walker (which Im not BTW), I would take a new dog out on his/her own for the first few sessions until we had a good working relationship and I had a better idea about that dogs temperament, personality, training, etc.
Of course this sort of thing does happen (sometimes inevitably). I dont think anyone is being blasé about it? But I also think some intelligent risk assessment and knowledgeable precautions minimize the risk of this sort of incident considerably.