Well, I disagree with that part. Spongebob and Patrick straight-out told him that he couldn't get into their treehouse, and Squidward climbed up there anyways just to defy them, and then when he climbed back out, he's the one who broke the vine holding their treehouse, thereby flinging them into the forest.Wait what?
First off, how does he freely choose to go to the forest? He is flung there against his will.
Second of all, the sheer fact that the Magic Conch doesn't allow him to eat anything IS abuse to him. The injustice of it showcases Squidward's bad luck, and a bad thing unfairly happens to him. THAT'S SQUIDWARD ABUSE! Bad things happening to him is Squidward abuse, bad luck that harms him is Squidward abuse on the writer's part, it doesn't just have to involve SpongeBob and Patrick doing it.
You can defend that you somehow find it funny, but the abuse is a 100% fact.