Let us look at the example he gives, to see if his own example stands up to scrutiny.
Mattix argues that "Just because the part of my brain associated with the leg and foot “lights up” when the metaphor “kick the habit” is used does not mean that the idea that freedom is good (which is what that metaphor evokes) is not true in some universal, “transcendent” way." I'm not sure why these two things have to be mutually exclusive. If, when anyone hears "kick the habit," the part of their brain associated with the leg and food "lights up," how is this not universal? It may not be "transcendent," but it is certainly universal in the only way that matters: for all humans everywhere at all times. Even if you don't have legs, you've seen people kick. So you can still understand the metaphor. So it seems to me that he is setting up a bit of a straw man in complaining that those favoring the "embodied" understanding of metaphor are arguing against universality. Against transcendence, perhaps, but then "transcendence" is not synonymous with "universal."
Next, Mattix quotes Donoghue about the effect of metaphor, that "The effect of Eliot’s metaphor is to give her a new, strange life."Yet, the theory of embodiment, again, does not dispute this effect. Yes, metaphors give us a new way of seeing things. Yes, metaphors connect two unlike things to create a new relationship. But the embodiment theory of metaphor is about the source of the two aspects being compared. It is not merely linguistic in nature, but rather represented as physical by the brain.
So if we look again at the lines by Eliot used:
A woman drew her long black hair out tightWe can note a few things here. One, unless you have experienced a fiddle/violin, you cannot be entirely sure what this means. When you reach the word "music," you can assume that "fiddled" has something to do with music. But does the action create music? Unless you know what a fiddle/violin looks like, you cannot be sure what the action looks like. So this line is only universal among those who know what a fiddle/violin is, how you play it, and what it looks like. The experience is necessary for the universality. And of course Eliot had to have experienced women, long black hair, tightness, fiddles/violins, music, and strings to make the metaphor in the first place -- and he had to have assumed others to have had those experience to even begin to understand his metaphor.
And fiddled whisper music on those strings
Finally, Mattix complains that we Literary Darwinists would end up discussing the connection between music and sex -- only to then make the argument that this line, and the lines before, are about sex! Certainly love is hardly discounted by Darwinists of any kind. Indeed, we Literary Darwinists would have likely come to the same conclusion as Mattix in regards to the passage -- only we likely wouldn't stop there, but continue on to discuss the evolutionary psychological reasons for why it is the case that sex with love is far more fulfilling than recreational sex. In the end, it seems that Mattix's complaint is that we don't stick to merely superficial explanations, but instead go deeper.
If that's his complaint against us, I'll take it. There are worse things to be accused of than that one's explanations are deep and complex.