Regarding Hillary Clinton and emails on her server, let us suppose that the statement made by HRC, I never sent or received classified information on my server, is true. We know that businesses have proprietary information that they do not wish to disclose. Bankers have information and banking laws that prevent them from disclosing "secret" information. And we know that the government has classified information it does not want to disclose, e.g. Snowdon et al.
So the question is, if it is true that HRC never transmitted or received classified information, how could she do her job as secretary of state? If her statement is true, then she would be incompetent. On the other hand, if the statement she made is false, then she is liar. Either way her words convict her and make her unsuitable for the presidency.