The teaching of the stages of life is responsible for immorality: it is no surprise that people behave like children given that they are taught they developed from children.
If the problem still needs to be spelled out, the fact that a person comes from an x does not necessarily make it an x, and does not necessarily make it "no surprise" when a person behaves like an x. If a person opts to behave like a child just because he knows he used to be a child, that is an indictment of him, not of teaching the stages of life. Likewise, if a person chooses to behave like an animal just because his remote ancestors were animals, that is an indictment of him, not of evolution or the teaching of evolution.
(ii) The argument suggests that there was no immorality before people were taught about evolution. A glance at a history book should be sufficient to dispel that absurd suggestion, since history is full of examples of die-hard creationists murdering one another and those unfortunate enough to get in their way.
Either that, or so great must the nefarious power of evolution be that its evil influence reaches even backwards in time to compel creationists to behave like animals long before Darwin walked the Earth.