I'm going to go out on a limb here and disagree with you :-D
I know that the Toastmasters folks will ding you for saying "Um" or "So", etc. And yes, if it is too common it can be annoying (sort of on along the lines of someone who inserts "you know" into almost every sentence). However, in this interview, it was obvious that you were doing that while trying to come up with a thoughtful and meaningful answer. I don't think that it detracts from the interview at all. In fact, I would say it is a sign of you being real, sincere -- and not just trying to BS your way through the interview.
I know that the Toastmasters folks will ding you for saying "Um" or "So", etc. And yes, if it is too common it can be annoying (sort of on along the lines of someone who inserts "you know" into almost every sentence). However, in this interview, it was obvious that you were doing that while trying to come up with a thoughtful and meaningful answer. I don't think that it detracts from the interview at all. In fact, I would say it is a sign of you being real, sincere -- and not just trying to BS your way through the interview.
My two cents.