Peter Pan is famously the boy who never grows up. If he did, he might have a more proactive attitude toward helping his female friends when they're obviously in distress. We don't know why Wendy tolerates him.
When Peter Pan takes Wendy to meet his mermaid 'friends' at the lagoon, the mermaids immediately attack her and try to drag her into the water. She looks to him for help, but he just laughs it off and says they were only playing. Thanks, friend!