Argument based on speculation

I was wondering if it is acceptable to argue a point that cannot be proven. For example; Person A states that majority of people on this earth have never stolen anything in their life. Would it be acceptable to argue against Person A using speculation as to why the majority of people have stolen at least once(human nature, etc)?

>>2

Perhaps I should have chosen a better example.

What if I was attempting to convince the reader that everyone has stolen at one point using only examples such as lack of security, human nature to want something for nothing, etc. Would this be defined as a weak argument?

I'm arguing against the statement: "Many of the people on this planet have never stolen." Specifically arguing that more people have than the author gives credit. I'm trying to convince the reader by explaining things that enable theft.