Realistically, there are three kinds of utility effects of someone choosing to install a NAT:
(1) The effect on them personally.
(2) The effect on other people who might potentially correspond
with them (a rather small set).
(3) The effect on the network as a whole, or to speak more
precisely, the effect on a large set of people who
have no relationship with the individual in question.
When I said "no strong argument" I was thinking about class (3), not class (2), which I agree there is a much stronger argument to be had about. I don't know of a strong argument for (3).
Vendors are forced to expend considerable engineering effort to support NAT users. I think this qualifies as a class 3 effect.
It would be interesting to see how much of the IETF's resources are used up by NAT issues. It must be a significant amount if a simple announcement about the advancement of IPv6 deployment turns into a discussion about the exact level of NAT's evilness.