In Acts 16, Paul takes on young Timothy as he continues his journey with Silas. Because Timothy’s father was well known to be a Gentile, Paul circumcised Timothy (16:3). We can only speculate that this was done so the preaching of the gospel among the Jews would not be hindered.
But in today’s reading, we find Paul taking the opposite stance on circumcision regarding Titus. While Timothy had a Jewish mother, Titus was a Gentile. Also, Paul was keenly aware of the Judaizing teachers, those who claimed to be Christians but sought to bind the Law of Moses on the disciples (cf Acts 15).
Paul well knew that in Christ neither circumcision nor uncircumcision accomplishes anything (Gal 5:6; 6:15). However, if uncircumcision would be a hindrance to the preaching of the gospel, Paul was willing to require it of Timothy.
On the other hand, because neither circumcision nor uncircumcision counts for anything, Paul would not permit Judaizers from binding it on followers of Christ as some test of faithfulness.
Galatians 2 also provides us a very unflattering picture of Peter. After noting that the preaching of the gospel to the Jews was given to Peter and the preaching of the gospel to the Gentiles was committed primarily to Paul, Paul openly criticizes Peter as a hypocrite for his withdrawal from the Gentile brethren.
Of all the people who should have stood up for the Gentile brethren, it should have been Peter (Acts 10-11). However, Peter wilted under the influence of James the brother of Jesus. How could this be if Peter was the chosen vessel of Jesus to lead the church after His ascension? How could the very “Vicar of Christ” be so cowardly toward his Gentile brethren? Didn’t James get the memo? Peter was the rock upon which the church was built (sarcasm).
No, Peter was neither the rock upon which the church was built nor the vicar of Christ, reigning as Christ on earth over the church.
Finally, I think it interesting that, after this confrontation with Peter, Paul himself was also unduly influenced by this same James, leading to several years of great difficulty for Paul (Acts 21:15ff).