If a person responds to a police tipline, say, with information overheard about a murder, and this information leads to an investigation, perhaps leading to DNA or other evidence against the killer, the accused killer does not get to face/cross-examine the tipster. Unless the tipster later becomes a witness. Who would ever respond to a tipline? And no one would fault the police or the DA for “conspiring” with the tipster to see where the evidence leads. There can be an accusation made on the tipline, but no one is conviction based solely on the tipline call.
It is obvious that in the impeachment proceedings, Republicans are purposefully conflating the word “whistleblower” with accuser. Trump should have the right to face the whistleblower (read: accuser). We should say that tipline responders are protected from dangerous criminals for good reasons.