Ephesians 310 That the manifold wisdom of God may be made known to the principalities and powers in heavenly places through the church,
Acts Of Apostles 20 28 Take heed to yourselves, and to the whole flock, wherein the Holy Ghost hath placed you bishops, to rule the church of God, which he hath purchased with his own blood.
Colossians 3 22 Servants, obey in all things your masters according to the flesh, not serving to the eye, as pleasing men, but in simplicity of heart, fearing God.
1 Corinthians 12 28 And God indeed hath set some in the church; first apostles, secondly prophets, thirdly doctors; after that miracles; then the graces of healing, helps, governments, kinds of tongues, interpretations of speeches.
1 Corinthians 14 19 But in the church I had rather speak five words with my understanding, that I may instruct others also; than ten thousand words in a tongue.
Matthew 16 18 And I say to thee: That thou art Peter; and upon this rock I will build my church, and the gates of hell shall not prevail against it.
Matthew 18 17 And if he will not hear them: tell the church. And if he will not hear the church, let him be to thee as the heathen and publican.
45 Ephesians 3 21 To him be glory in the church, and in Christ Jesus unto all generations, world without end. Amen.
2
The Eastern Church Defends Petrine Primacy and the Papacy
St. Peter, Bishop of Alexandria (306-311 A.D.): he became bishop around A.D. 300, reigning for about eleven years, and dying a martyr’s death. Peter, set above the Apostles.
St. Anthony of Egypt (330 A.D.): Peter, the Prince of the Apostles (Anthony, Epist. xvii. Galland, iv p. 687).
St. Athanasius (362 A.D.): Rome is called the Apostolic throne. The Chief, Peter.
St. Macarius of Egypt (371 A.D.): The Chief, Peter. Moses was succeeded by Peter, who had committed to his hands the new Church of Christ, and the true priesthood.
web.globalserve.net/~bumblebee/ecclesia/patriarchs.htm
staycatholic.com/the_pope.htm
St. Irenaeus (Adv. Haer., III,3) which brings out in fullest relief St. Polycarp’s position as a link with the past. It was possible to learn by word of mouth what the Apostles taught from those who had been their hearers. In order then to know what the Apostles taught, we must have recourse to the “successions” of bishops throughout the world. But as time and space would fail if we tried to enumerate them all one by one, let the Roman Church speak for the rest. Their agreement with her is a manifest fact by reason of the position which she holds among them ("for with this Church on account of its potior principalitas the whole Church, that is, the faithful from every quarter). From the Roman Church, representing all the churches. St. John, the Apostolic Age had been prolonged till “the time of Trajan”. Of Polycarp he says, "he was not only taught by the Apostles, and lived in familiar intercourse with many that had seen Christ,
newadvent.org/cathen/12219b.htm
Theodore of Beza wrote: “What crime can be greater or more heinous than heresy, which sets at nought the word of God and all ecclesiastic discipline? Christian magistrates, do your duty to God [speaking in Calvin’s Geneva of 1554], who has put the sword into your hands for the honor of His majesty; strike valiantly these monsters in the guise of men.” He went on to characterize those who demanded freedom of conscience “worse than the tyranny of the pope. It is better to have a tyrant, no matter how cruel he may be, than to let everyone do as he pleases.”
Calvin sought to persecute heretics (particularly Roman Catholics) so as to keep Protestant believers in the lands divided by the Reformation faithful to his new teachings.
The Lutherans proclaimed in full synod:
“The Zwinglians . . . we do not even grant to them a place in the church, far from recognizing as brethren, a set of people, whom we see agitated by the spirit of lying, and uttering blasphemies against the Son of Man.” (113;v.1:466)
The Zwinglians believed that the Eucharist was wholly symbolic (probably the majority position of Protestants today). Hence, whoever believes the same would have had the foregoing said about them by Dr. Luther, who firmly held to Consubstantiation, i.e., the actual Body and Blood of Christ is present in the communion along with the bread and wine.
- Luther on Protestant “Heretics”
“Heresiarchs . . . remain obdurate in their own conceit. They allow none to find fault with them and brook no opposition. This is the sin against the Holy Ghost for which there is no forgiveness.” (51;v.6:282/24) “Those are heretics and apostates who follow their own ideas rather than the common tradition of Christendom, who . . . out of pure wantonness, invent new ways and methods.” (51;v.6:282-3/25)
catholicapologetics.info/apologetics/protestantism/protin.htm
Ok there are some other reasons too. 
