"See what large letters I use as I write to you with my own hand!" NIV translation
Paul had a problem with his eyesight and so many of his other letters were dictated to someone else to write down. He calls the reader to notice that this letter was written in letters that were much larger than normal as a sign that he wrote it down personally. (It would have been impossible for him to write smaller and still have it be legible)
Once again, we see the battle between the physical eyes and the spiritual eyes. Paul is describing Christian leaders who are more interested outward appearances (physical eyes) than the well being of those God has placed in their care (spiritual eyes). These leaders did not have the courage to stand up to the pressure from society and so were bending to legalism and falling from grace (see chapter 5). Because Paul speaks of circumcision here, we are quick to pass over this verse and say it does not happen today but the same sort of legalism is at work in the church. Many spiritual leaders have gotten caught up in a numbers game and so have built larger and larger buildings that must be filled. Many of these leaders will then compel "members" to be there or risk their salvation and say that they will "fall from grace". This is a perversion of the Word and legalism just as was happening in Paul's day.
"Not even those who are circumcised obey the law, yet they want you to be circumcised that they may boast about your flesh." NIV translation
Paul warns the Galatians that the judaizers are only following part of the law and they do not even care about the people. We see that their motive was not bringing people closer to God but being able to brag about the number of conversions.
Although circumcision is not an issue in the church today, legalism has still crept in and many leaders have the same motives as the judaiziers. Many leaders want to build a mega-church building and brag about the number of people that attend their services without even caring about whether they come to faith in Jesus Christ or not.