I assume that we're talking about opinions on factual matters, not personal values. Yes, one's fundamental (terminal) values I would expect to be pretty stable.

To my thinking, this stance forfeits rational reflection where it really counts most. You're saying, if I understand you, that you respect people who change their opinions on factual matters, but not on questions of fundamental ethics. This seems to assume, among other things, that people's values are much more coherent than they are (leaving little leverage for change).

You lose much more status, it is true, when you re-evaluate your terminal values than your factual contentions. That just means the problems of self-confirmation are compounded in ethics, not that they should be ignored there. You can't be rational yet rigidly maintain your terminal values' immunity to rational argument.