It never ceases to amaze me how incapable Catholics are of understanding that others do not follow men as Catholics do.
They simply cannot wrap their minds around the fact that followers of Christ follow CHRIST, not a human stand in for Him.
Inasmuch as they have faith in Christ, repent of their sins, and keep the commandments, they are followers of Christ.
Inasmuch as they follow doctrines of men, like Sola Scriptura, they are followers of human tradition.
This is why Christ's Church teaches that followers of Luther are imperfectly united to the Body of Christ, to varying degrees.
"If he will not listen to the church, treat him as a pagan or tax collector." --Jesus
Jesus gave His Church, the "pillar and foundation of truth," the Authority to teach and to discipline --to bind and loose. Christ did not give this Authority to Luther or Calvin, or any of their disciples.
"Go and make disciples of all the nations... teaching them everything I have commanded you." --Jesus
If Protestants followed Christ, they'd do what the Bible says instead of bending it to fit one of their (depending on who they follow) doctrines.