It's totalitarian if the government does it. Private citizens are allowed (Free Speech) to make private judgments of this sort, even if their reasoning / conclusions are ludicrous or unsavory.
Indeed. And there are formal procedures to, and both legal and administrative oversight over, those investigations.
It's not appropriate for the Chief Executive (far less an unappointed private citizen, in charge of an ad hoc advisory body) to have arbitrary un-auditable access to every citizen's financial records.
IRS is indeed horrifying.