Hearsay is not necessarily a lie, but it is not credible evidence either.
Since it looks as though this red herring of hearsay (in an investigation) is not going away, let's all make sure we understand what is acceptable.
If a witness, Robert, in court states "John told me so and so" this is fine as long as John is also available as a witness in the trial. It is not admissible if the court will have no opportunity to question John. In that case it would be inadmissible hearsay evidence. Further, the court might well agree to consider the report of what John said if John should have been available to testify, but never appeared.
In the current inquiry (not trial remember) in almost all cases, the other party in reported conversations should be available, except that the President has ordered them not to appear, and it would take several months, at least, to get final court decisions to enforce their appearance. Since almost everyone states (truthfully or not) that they want the impeachment inquiry completed as quickly as possible, this means that the inquiry will not hear from many of the most important witnesses.
[For those who believe that an inquiry should follow all the rules that are applied in a trial, note that this would invalidate almost all police use of informers, and would also make it inappropriate to respond to a report of someone screaming for help from the window of a building.