I can talk from the perspective of three different sects within the broader scope of Protestantism. That would be Presbyterian, Baptist and Episcopalian traditions. The Presbyterians would feel that it is no one’s business but the immediate church’s session, but, if it gets too carried away, they’d have to kick it up to the various levels above.

Baptists would feel it’s no one’s business but their’s and start a break-away church.

Episcopalians would think you were heretical and make you a Bishop.

I’m referring, of course, to radical differences in doctrine, like denial of the Virgin birth or the diety of Christ.

If it was lesser — infant baptism, say — they would pretty much remain the same, with the exception that the Episcopalians would privately wonder why you haven’t changed churches since you’ve obviously become a fundamentalist.