Do you have quotes from them as to why they left the Catholic Church that would demonstrate they held this position? Do you have any evidence that any Protestants state this, or is this your inference (subject, conceivably, to correction)?
Martin Luther: "Since then your majesty and your lordships desire a simple reply, I will answer without horns or without teeth. Unless I am convinced by Scripture and plain reason- I do not accept the authority of popes and councils, for they have contradicted each other- my conscience is captive to the Word of God. I cannot and I will not recant anything, for to go against conscience is neither right nor safe.”
givemethatbook.com/martin-luther-his-quotes-on-scripture/
“[It] is an accursed lie that the pope is the arbiter of Scripture or that the church has authority over Scripture. This is what the canonists and commentators on the Sentences have wickedly declared”
Miscellaneous Remarks on Scripture by Martin Luther"
" Personally I declare that I owe the Pope no other obedience than that to Antichrist.”
gty.org/blog/B130226/exposing-the-heresies-of-the-catholic-church-the-pope
John Calvin: "Although your Letter has many windings, its whole purport substantially is to recover the Genevese to the power of the Roman Pontiff, or to what you call the faith and obedience of the Church. But as, from the nature of the case, their feelings required to be softened, you preface with a long oration concerning the incomparable value of eternal life. You afterwards come nearer to the point, when you show that there is nothing more pestiferous to souls than a perverse worship of God; and again, that the best rule for the due worship of God is that which is prescribed by the Church, and that, therefore, there is no salvation for those who have violated the unity of the Church unless they repent. But you next contend, that separation from your fellowship is manifest revolt from the Church, and then that the gospel which the Genevese received from us is nothing but a large farrago of impious dogmas. From this you infer what kind of divine judgment awaits them if they attend not to your admonitions. But as it was of the greatest importance to your cause to throw complete discredit on our words, you labor to the utmost to fill them with sinister suspicions of the zeal which they saw us manifest for their salvation. Accordingly, you captiously allege that we had no other end in view than to gratify our avarice and ambition. Since, then, your device has been to cast some stain upon us, in order that the minds of your readers, being preoccupied with hatred, might give us no credit, I will, before proceeding to other matters, briefly reply to that objection.
monergism.com/thethreshold/sdg/calvin_sadolet.html
“Some persons think us too severe and censorious, when we call the Roman pontiff Antichrist. But those who are of this opinion do not consider that they bring the same charge of presumption against Paul himself, after whom we speak, and whose language we adopt. And lest anyone should object, that we improperly pervert to the Roman pontiff those words of Paul, which belong to a different subject, I shall briefly show that they are not capable of any other interpretation than that which implies them to the papacy”
gty.org/blog/B130226/exposing-the-heresies-of-the-catholic-church-the-pope
) but aren’t you once again implying that I said something negative about you, but without saying what it is? 
