I don’t think Pierrot would allow the humans to do anything bad to Columbina. Remember that’s exactly how they ended up in that situation in the first place. Some humans showed an interest in her and Pierrot stepped in to protect her. But then they injured him so badly that he was left unable to move, likely near death and for what was likely the first time in their captivity, he couldn’t protect her from anything. Columbina, then turns to Harlequin for help who takes advantage of the situation to provide the others and himself with food for strength to turn on their captors. It could be that Harlequin thought he was protecting her in a twisted sense but my interpretation was that Harlequin might have been insulted by the request. Perhaps he found it audacious for her to expect his protection when she had chosen Pierrot over him. And only once Pierrot can’t protect her does she turn to him for help. He may have thought “You aren’t mine to protect so why should I protect you when the rest of us are starving and you’re the weakest one. Instead..why don’t YOU save US by giving us the strength to fight back?” Obviously this is a very negative interpretation of the events and may not be correct. Even if it is, it might only be partially correct as I’ve realised that Harlequin is extremely complicated and difficult to read. There’s probably multiple reasons why he does things and not a straight forward answer. The creator has said that when it comes to harlequin, even when out right says how he’s feeling/thinking you don’t know if you should believe him or not.
Oh my God...! I feel like I just had an epiphany with your theory. I'm taking your interpretation (if you don't mind and not as my own of course) to further understand the story and its characters; it might as well be true! Allow me to share:
In the commedia dell'arte, Columbine chose Harlequin over Pierrot, but in this story, Columbina chose Pierrot. The role of Columbine is a soubrette which is not exactly what Columbina was portrayed -- more of an ingénue. I thought that Neko just decided to go on with his story and not follow exactly the stock character, but it does make sense: Colombina has chosen Harlequin in the end for she has turned to him for protection (despite rejecting him all this time). Thus, she probably didn't love Pierrot for what he is but mostly for the attention, gifts, and protection he was offering... And so it was easy for him to get replaced: all she cared about was to live, not him...
That is just insane because then it would make Pierrot's character more tragic (as it already was), defend Harlequin's actions (just a little since it explains why the rest were not so fond of her/why it was so easy for them to be okay with her death -- she was exploiting Pierrot and lead him to agony), and tell more about Columbina's true character.Not even a monster could love Pierrot... This is of course just a theory and personal speculations. Thank you for sharing this with us @Princess Spooky Suki! KUDOS ❤