Perhaps I’m a cynical bastard, but I just don’t think people are primarily motivated by empathy but rather by interest.
The opposition of interest and empathy is an interesting one - I think it is a mistake to see them as being mutually exclusive.
For interest/empathy we can more or less substitute cognition/affect. If we do this we see that these are less terms in opposition and more psychological categories (so, parts of a whole). The point is that, if we divide the psyche up like this, both parts are involved in any event - including political and economic decisions.
Alberto Toscano's recent article 'Powers of pacification: state and empire in Gabriel Tarde' (which I read yesterday so it's fresh in my mind) makes an interesting point: the likes of Tarde (alongside Whitehead, Deleuze, etc.) who have recently been revived because of the central place they give to 'emotion' in metaphysics (and thus politics) have been hailed as displacing the reductive rationalism of neoliberal economics (and so most sociology and political science, too). But what Toscano points out is that this is only one side of the story - the side of the economists; the other side is that of the marketers - on this side, from Edward Bernays and Walter Lippmann through to our PR obsessed present, the place of 'affect' has been pivotal (and it has always been associated with anti-democratic sentiments). Deleuze and Guattari weren't the first to describe capitalism in terms of desire - this had been going on for decades.
On this issue I would highly recommend Adam Curtis' documentary 'The Century of the Self (my favourite documentary of all time, in fact) which charts the trajectory of 'affect' through Western society from Freud's psychoanalysis through 60s/70s 'rebellion' to Bill Clinton's PR/market research fueled election campaigns.
All of which is a long winded way of saying that I don't think we have to choose either interests or empathy - it is in the interaction between interests and empathy that politics is to be found. The point that Ian mentions about Lakoff being a "60′s hippie flowerchild" is quite right and Curtis' documentary shows precisely the links between this kind of quasi-political subjectivity and the corporate politics of the present. Whether he is "increasingly out of place in the 21st century" is a more complex question, however. Far from being 'out of place' as such I would see his statements as standing for much of what passes for the 'left' in the U.S. today - that is, a remnant of bygone 'glories' that weren't actually all they were cracked up to be in the first place and still pervade the emotive focus of present discourse. In other words, the centrality of 'affect' or 'empathy' just places all the weight on one side of a, if not arbitrarily then certainly inexactly, partitioned psyche.
The right in the U.S. and elsewhere are under no such illusions - they are more than happy to play on both sides of psychology and be thoroughly instrumental in doing so. (See William E. Connolly's book 'Capitalism and Christianity, American Style' for an account of how the right is able to organise and cooperate even when it is profoundly divided internally between neocons, neolibs and evangelicals, etc.)
The interesting point, if we go back to Toscano's article, is that this 'affective leftism' so prominent in U.S. politics is also present in 'leftist' academia (hence the new popularity of Tarde, etc.)
Now that doesn't mean that I don't think Tarde, Whitehead, Spinoza and the others aren't important but (actually, like Spinoza) we need to rethink the relationship between emotion and rationality rather than just placing all the weight on one side over the other.
In short: neither interest nor empathy rules a priori - the 'left' is doomed so long as it dwells on either half; the right doesn't make this mistake.