I really love this. Lexington has had time to sit with the fact The Pack has escaped, and he hasn't come down from his mission. He isn't caring about high mindedness right now. He cares about his vengeance. And. I think. He tells himself he cares about keeping The Pack from hurting anyone else. They have a platform, they sell themselves as the good guys, people will come trying to get autographs from them as they are hunting down people who haven't hurt anyone.
The Pack is dangerous. In part because they are able to pretend as though they wouldn't be so to anyone who was good or innocent, but that's not true.
It really works in this sense that this is the first episode after their declaration that Manhattan is their castle. Demona, so far as they have seen, is a danger to their clan, not so much to the humans they're now protecting. But The Pack? He's got all he needs to work with to make this seem bigger than just his simple revenge. And no amount of "think about what's important like family and friends etc" is going to deter him.
But he can't explain how this feels different to Brooklyn and doesn't want to use the energy if he felt he could. So he dismisses this conversation.
I think Brooklyn wouldn't want to come off so cold hearted to everyone with such a dismissal if that argument was used against him, and so that's the tact he's taken with Lexington. He's worried about him for good reason but doesn't see how what might work on him might not for Lexington.
I love this moment. I love Brooklyn for trying and the compassion he shows. I love the way Lexington coldly rejects the attempt at camaraderie and advice. And I love that Brooklyn straight forwardly tells him how concerning he finds that. Just... overall a really great character moment. XD