In "I second that emotion" its clear that Bender doesn't know what a toilet is used for because when he's trying to flush himself down the toilet to get Nibbler, he says
"What do humans design this thing for anyway?"
But in the part where Leela asks him how he could do such a thing he says
"Well I had to lift the seat up first, that was the first little annoyance am I right men?"
But if he didn't know what the toilet was designed for, he shouldn't know why guys lift the seat up
If that makes sense..I'm sorry if its complicated to understand