The laugh was a bit of a relief, honestly. Not because he minded so much being dangerously close to kissing Barry Allen. That, in fact, wouldn't have been so bad. It was still on his to do list, actually. Now that he had some honest reciprocation going on. But the laugh was more important because he needed some contrast to the earlier tone of their conversation. Confirmation that even though Barry was down, he wasn't out. Although it would probably surprise Barry and his friends to know this, Len did care about the kid in his strange way of caring about things in general. Barry Allen, and his alter-ego for that matter, had become central to his sense of motivation. First because The Flash made him a better criminal but now also because Barry Allen was possibly making him a better human being. Loathe though he was to admit it.
So, yes. He maybe didn't have it in him to make Barry utterly miserable anymore simply because he was the Flash, but making his life more difficult was still very much on the table. As Captain Cold, primarily. Leonard Snart maybe had very different motivations were Barry Allen was concerned.
He smirked in the face of that laugh, though it lacked some of the sharper shark-like edges he tended towards. He was still very proud of himself. It was no easy task making a literal crippled joke and having it land but, well. He was good with timing. Especially where puns were concerned. If Lisa were around she would have probably called the particular expression he was wearing fond, which was just another reason to be greatful she wasn't around to bare witness to any of this.
"I pride myself in the ability to be one, yes. Goes with the territory. Criminal. Rogue. Asshole. Though," he dropped his eyes down to where Barry's hand had been vibrating on his arm just moments before. "I might have it in me to be less of one if you ever want to show me just how many different places you can vibrate like that."
He very purposely hadn't moved from his place braced on Barry's chair. The proximity was still intentional and while he considered the laugh an accomplishment, he still had other intentions.
"Back to something more important. What you and West were saying earlier. Open relationships. That true? Because I'm a very good liar, and a criminal, but not a cheat."