I have never been in a startup that fears arguments. Every startup I have been a part of has lively debates and arguments almost every other day. It's only the large slow moving corporate giants where I see such lack of debate and arguments on what is obviously wrong.
I would go to the extent of saying that a startup that does not encourage arguments in a harmonious fashion would die very soon anyway. Debates and arguments help in weeding out stupid ideas and focus on what that really matters.
This person's email shows that he can have a qualitative argument in a coherent, polite, and non-confrontational fashion - exactly the kind of people you need in startups!