Albert Barnes on Titus 3:11

Knowing that he that is such is subverted. Literally, is turned out; or, is changed, i.e., for the worse. He has gone from the right way, and therefore he should be rejected.

And sinneth, being condemned of himself. His own conscience condemns him. He will approve the sentence, for he knows that he is wrong; and his self-condemnation will be punishment sufficient. His own course, in attempting a division or schism in the church, shows him that it is right that he should be separated from the communion of Christians. He that attempts to rend the church, without a good reason, should himself be separated from it.

(+) "condemned of himself" "self-condemned"