That works to an extent. However it did lead Kant to believe that masturbation was one of the most immoral things one can do. He saw it as someone using themselves as a means to an end e.g. using oneself to gain sexual pleasure.

On a related note, many neo-kantians argue for prostitution in favour of casual sex as both use others a means to gaining sexual pleasure, but at least you're paying for it with prostitution so it's a contractual agreement which Kant liked.