Morality is a very complex topic that possibly can't be proven by logic anyway. Why is racism immoral, other than the fact that we, as a society, have decided that it's immoral?
I think seduction manuals are immoral because they essentially treat women like min-maxers do video games--do this, and your chance of success is raised by X%, follow this procedure to succeed, etc. It makes women into vending machines that, if the buttons are properly pressed in the right succession, will theoretically result in a prize--sex--being dispensed. I think that treating people like that is immoral. Can I prove this logically? Can I claim that this is a universal truth? Of course not, but the same is true for every moral stance.
I think seduction manuals are immoral because they essentially treat women like min-maxers do video games--do this, and your chance of success is raised by X%, follow this procedure to succeed, etc. It makes women into vending machines that, if the buttons are properly pressed in the right succession, will theoretically result in a prize--sex--being dispensed. I think that treating people like that is immoral. Can I prove this logically? Can I claim that this is a universal truth? Of course not, but the same is true for every moral stance.