I am diabetic and the only one that i know of that does not happen is recurring infections unless you have very easily bruised skin and then maybe it can happen if you get sick or something
Contamination usually occurs when draping an extremity.
The most clear way would be - "Sam, I don't think stealing things from a shop is ok, it's illegal and you're stealing away the hard work of some people without paying for it".
That should send Sam a clear message that will explain him why stealing is wrong and why he shouldn't be tealing in the first place.
