One thing I read somewhere else that really resonated with me is that Hook's last true love, Milah, had her heart ripped out of her chest and died in front of him. So it's not just that Emma's heart can be broken and therefore can also love. It's that she still has a heart in the first place. And also remember his comment about saving Emma from a loveless marriage, something he actually already has done once before with Milah.
Even though we don't hear much about Milah and Hook's revenge anymore, we also know how much TPTB love their parallels on this show. So it could get very interesting as Captain Swan progresses to see how Hook's relationship with Milah manifests itself in this new potential relationship of his.