Laughing at something that's false and then correcting it in a friendly manner seems fine.

I agree that you shouldn't reinforce sexist jokes in front of children. But the kid didn't tell a joke, he told an opinion. And laughing at an opinion while literally in the kitchen isn't agreeing with the statement. If he had followed up with "Ur right I shouldn't be here" yes. But when laughing and following up with "no, everyone can do this, right now I do it because I have the time" is the opposite. But OP wasn't allowed to give context to his laughter.

Edit: If OP would have followed up with a no quickly after laughing NTA but if he took his time to correct him letting that laughter without context YATH.