That I can't argue with, though it wouldn't follow from that that UCMAs are likely to be false.
EDIT: you edited your post, and so my reply doesn't seem to make sense. In answer to your new question, I would say 'I don't, I just want some presentation of the argument on which its validity (or invalidity) is obvious'.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.