Dr W, I think we can agree that there is no simple answer to these things.
If I perform Leach's analysis on another, but similar, Beatle song, I get a conflicting result. According to Leach the tonic is positive, the subdonimate calls for our attention, and the dominate is negative.
These are the words that fall on the chords changes in the first verse of Let it Be.
dominate (positive): find, speaking, in
subdominate (attenttion): comes, be, front
dominate (negative): times, wisdom, darkness
Yes, darkness is negative, but wisdom isn't. The words find, speaking and in are neither positive or negative. The words comes, be, and front are not really demanding attention.
Leach is making a generalization akin to major chords are
and minor chords are