sid represented our repressed need to demonstrate what happens too overlords who treat their plebs toys with disregard. The scene where the tortures the army men? Not an entirely veiled cry for revolution.
What made Sid a good character is that there was a real depth to his symbolism.
The downtrodden and oppressed toys? Just similes for the people who were used and thrown away and then never forgot.
The problem with that line of though is that’s more of a meta thing, Sid being a character in a story representing an idea outside of it.
Within the story, you suggested the kiddiwinkles give the toys life by essentially believing their alive.
Sid created the Frankenstein-toys, and it would be his belief (perhaps his sister’s?) that gives them life. Why do the toys rebel against him, as their creator? If he’s the one imagining them, he’s the one that gives them their personality. If their personality is to effectively overthrow him for what they might see as torturing them, what does that say about Sid?
Nah, Sid has such low self-esteem that even the creations he controls in his head don’t like him. Unless it’s his sister doing the believing, but then we need to consider at what point control over the identity of a toy is transferred between people. Does his sister retain control because the toys were her’s in the first place, or does Sid now have control of them as he made them?
An interesting thing to consider as the Frankenstein toys help out Buzz by repairing his arm.