If the lawyer is correct and the search warrant is invalid won't any evidence found at his home will be inadmissible in court?
The author of that letter claims to be the "legal representative" of his company which he also serves as Chief Operating Officer. An officer of a corporation is, legally, authorized to speak for and represent the company, so it's hard to know if he is claiming to be the company's lawyer. Unless he is a graduate of the esteemed California Close-Cover-Before-Striking School of Law, it is difficult to believe he passed the California bar exam.
In any case, he is citing a provision of the California Penal Code that exempts journalists from being compelled under threat of being held in contempt of court to reveal their sources. That is not the same as protecting a person suspected of receiving stolen goods from the execution of a search warrant signed by a judge seeking physical evidence of a crime.
A press pass is not a license to steal, nor is any reporter excused from the commission of a crime in the name of journalism.