Wonderful question. Definitely up-voted!
Right off the bat, I'd like to nip the tendency to equate altruism and empathy in the bud. I'm not saying that the questioner is making this equation, but that I've seen it at work in discussions with more so-called socially-minded peeps, anarchist or not. Using egoist language, altruism is spooky; empathy is far more sensual. Altruism has a tends increasingly toward the abstract at play in logic, argumentation and the psychological tyranny of morality, not necessarily in that order.
Empathy, on the other hand, may be likened to arousal, welling up uncontrollably, embodied. It is apt to say, 'I'm moved' or 'I'm touched.' I realize this may be a simplistic binary model, not able to plumb the depths, but I do find it a useful, if only provisional.
For me, there's no such thing as empathy, but the word serves for a host of feelings arising always from somewhere at once similar and familiar. Now, these feelings may manifest in ways which others may label as altruistic, sometimes they don't. Empathy doesn't negate all senses of cruelty, after all, any more than a joyful life does. As such, I find these feelings contextual, not necessarily anthropocentric, and sometimes inter-plays in weird ways with so-called non-living 'things' which at first glance most people would think of as an object. Take this very-short story attributed to Hemingway, 6 words in fact:
"For sale: baby shoes, never worn."
Where does it take you? I recall what I felt the first time I heard this, for I feel it in some way every time I hear this. The feelings aroused over a presumably 'non-living thing.'
Deeper still, I tend to feel those empathetic springs well up most intensely with those I've known for longer and with whom I choose continued play. It seems pretty obvious I 'value' these relations. They make up a great deal of my life, after all. One might say we re-spirate one another by way of mutual in-spiration. A deeper sense of mutual aid indeed.
When socially-minded types invoke the specters of altruism, I sense a presupposed notion of mass-social scales underlying the invocation, and I question whether or not those invoking have deep connections with others and/or are always on the move, never settling long enough for formations of empathy. With the latter I have no issue with per se, but when the preaching begins on how others should live, they've lost me to be sure.
In sum, I think it may be important to have socially-minded anarchists take some of the burden of demonstrating where they're coming from in using notions like 'empathy,' 'better future,' 'values,' 'good,' 'society,' rather than taking on that burden readily for them and unilaterally. I've not been fooled so much by these words for a while now, and at times have grown weary of, and irritable toward, the expectation to explain myself within a simplistic framework of 'good society/bad individuals' or some somber dirge like it. All in all, no one has a monopoly on these feelings. I simply feel them in one, unique, way.
Edit for clarity and again.