It seems most likely that a majority of the derogatory remarks you hear in regards to root canal treatment must be including in them references to that period of pain and discomfort the person experienced leading up to their need for treatment. In fact, in some cases the entire root canal process could be completed without any anesthetic or pain. Simply because in these cases the nerve tissue in the tooth has died. Dead nerve tissue cannot transmit pain sensations. Most likely, and especially if ask them to.
Nobody likes a bad time.
Not you, not your dentist. Just so things go as smoothly as possible and so there are no surprises, most dentists will go ahead and numb up any tooth on which they are performing root canal treatment. Remember, your dentist is trying to perform treatment which will hopefully last you a lifetime. They need to be able to concentrate on their work and not on how you are reacting to it. If they numb up your tooth both of you will be more at ease and relaxed.