Fans on Reddit aren’t just looking for justice for Kingler, they’re also noting all of the times that Ash has acted similarly giving the same treatment to other Pokémon including his Muk and Tauros.
Some fans suggested that perhaps he is catching these Pokémon simply to troll Professor Oak, and given his decision making this could be a likely explanation.
You can read the referenced thread in full on Reddit. I agree with the sentiment though; the Krabby was mistreated from start to finish and deserved better. But you could say that about so many of Ash’s Pokémon.