About two years ago, it very much felt like freedom from authority was a terminal value for me. Those hated authoritarians and fascists were simply wrong, probably due to some fundamental neurological fault that could not be reasoned with. The very prototype of "terminal value differences".

And yet here I am today, having been reasoned out of that "terminal value", such that I even appreciate a certain aesthetic in bowing to a strong leader.

On what basis do you assert you were "reasoned out" of that position? For example, what about your change of mind causes you to reject a conversion (Edit: not conversation) metaphor?

If that was a terminal value, I'm afraid the term has lost much of its meaning to me. If it was not, if even the most fundamental-seeming moral feelings are subject to argument, I wonder if there is any coherent sense in which I could be said to have terminal values at all.

Yes, that's the problem with the conversion metaphor. If reasoning does not cause changes in terminal values, then it seems like terminal values are not real for some sense of real. Yet moral anti-realism feels so incredibly unintuitive.

Edit: The other way you might respond is that you have realized that you still value freedom, but have recently realized it is not a terminal value. But that makes the example less useful in figuring out how actual terminal values work.