As to Gal: 5-11, I feel this gets the point accross better, incase someone is misunderstanding it:

11 if I were still preaching that you must be circumcised--as some say I do--why would the Jews persecute me? The fact that I am still being persecuted proves that I am still preaching salvation through the cross of Christ alone. 12I only wish that those troublemakers who want to mutilate you by circumcision would mutilate themselves.[b]" New Living Translation

Paul isn't saying that he IS teaching the need for circumcision. What he's saying is that IF he was teaching the need for circumcision, why would he still persecuted? By teaching circumcision he would not offend the Jews because he wouldn't be saying they are saved through Jesus.

He is saying he is persecuted because he is teaching that there is no need to be circumcised, and this is offensive to the Jews.