In the professors case, as he gets more comfortable, he can always find ways to alleviate any issues students may have like notes and good references to the material and so much more.  We have had issues with fluent teachers that had tenure and were difficult enough as it was.  I have also seen ted talks from stutterers who spoke very eloquently and other interviews were stutterers stuttered but understood and were empowering.  So I think its right and we'll worth it for stutterers to do anything.  Keep in mind it is not consistant and tends to change over time and with comfort so why draw a line earlier?