"Slander and libel is not acceptable but, not being a legal expert, I cannot comment on whether such an act was committed."

You do not need to be a legal expert to recognise an unsubstantiated accusation.

An unsubstantiated accusation is not at all the same thing as slander or libel. An unsubstantiated accusation may well be true. "Unsubstantiated" does not mean "false". Dictionaries are available for the use of the uncertain.