Alaric isn't able to process Lenore's words. Not right away. He knew that being told about another life she doesn't remember was a shock to her—it was a shock to him, too. But he never thought about how the details would feel from her point of view. How could he even begin to pretend he knows or understands what she's feeling about this revelation?
But maybe the problem was that he focused on his own confusion and cared for Lenore's physical state without taking the time to consider what it must feel like to be told that she lived in the past as a beloved soul, and the earth simply reapplied the mark on her new body when it had the chance to do so. It should be an honor, and Alaric knows the priest who learned about it saw the mark as such. As the Temple taught him to.
Unfortunately, Alaric has never known the mark as anything other than a curse. Being loved isn't always a positive thing, especially if that love is connected to any sort of divine spirit.