“If Luther held to something, like Baptism, he said that those who don’t follow it are vile. But Baptists (for one) disagree with him”
God used blessed saint Luther to recover the Gospel of Grace and so much more.
That doesn’t mean he was infallible.
My point being that Luther was pretty much “my way or the highway” - and most of those who call themselves “Protestants” don’t follow his way in most ways :)