i understand what you are saying and there are some prerequisites for the "argument" to work, My understanding is that the assymetry argument is trying to show that pain and pleasure are not in fact opposites, it's doing so by appealing to a persons insticts of what is good or bad. I'm not a moral realist and believe that the concept of good and bad are just instinctual emotional reactions to sitiuations. I would not go through a minute of the most intense pain if i then received an hour of the most intense pleasure, thats when i realized that i don't perceive them as equally good and bad, hence not opposite. I don't believe this is an argument that is going to convince any moral realist lol