As far as Judaizers go, since Paul accused Peter quite publicly of that, I would say that we are to name names about that.
Here's more about the Judaizers:
Galatians 5:19-26 The acts of the sinful nature are obvious: sexual immorality, impurity and debauchery; idolatry and witchcraft; hatred, discord, jealousy, fits of rage, selfish ambition, dissensions, factions and envy; drunkenness, orgies, and the like. I warn you, as I did before, that those who live like this will not inherit the kingdom of God. But the fruit of the Spirit is love, joy, peace, patience, kindness, goodness, faithfulness, gentleness and self-control. Against such things there is no law. Those who belong to Christ Jesus have crucified the sinful nature with its passions and desires. Since we live by the Spirit, let us keep in step with the Spirit. Let us not become conceited, provoking and envying each other.
Galatians 2:14 When I saw that they were not acting in line with the truth of the gospel, I said to Peter in front of them all, “You are a Jew, yet you live like a Gentile and not like a Jew. How is it, then, that you force Gentiles to follow Jewish customs?
(literally, to Judaize, that is, to keep the ceremonial customs of the Jews: What had been formerly obedience to the law, is now mere Judaism). Jamieson, R., Fausset, A. R., Fausset, A. R., Brown, D., & Brown, D. (1997). A commentary, critical and explanatory, on the Old and New Testaments. On spine: Critical and explanatory commentary. (Ga 2:14). Oak Harbor, WA: Logos Research Systems, Inc.
Note also Peter's response to Paul's rebuke. It was the response of a true Christian, not of a false one, which we have so many of now:
Paul severely and publicly rebukes Peter for his inconsistency and his insincerity. The rebuke was as wide as the relapse. Paul, vested with divine authority, took Peter to task. Paul’s unsparing, but tactful, rebuke of Peter reveals his apostolic independence of all human authority. Peter did not try to defend himself, but graciously accepted the well-deserved rebuke and later referred to “our beloved brother Paul” (2 Pet 3:15–16). Livest after the manner of Gentiles.Not under the customs and restrictions of the Jews. Peter’s habit had been to live according to Gentile ways, although he was a Jew by birth. With this as a condition, Paul asks Peter a pointed question. Why compellest…? Indirect compulsion by his example, not by false preaching. He was guilty of compromising conduct by which he was obliging the Gentiles to Judaize, to adopt Jewish customs and observe Jewish statutes. KJV Bible commentary. 1997, c1994 (2380). Nashville: Thomas Nelson.
Keep in mind too that today not all judaizers are true Christians, many simply call themselves that. The example of Peter and Paul is one of someone who was a true Christian, but there are those who do this that haven't got the foggiest notion of what it means to be a true Christian and as such again, are not our brothers or sisters in Christ. Here's more info about the judaizers: (I'm including this both for myself as a reference and for others who may not know about them)
Some may object to the use of the word dualism for what the apostle is describing here. The word is appropriate, however, if we understand it is a modified dualism. It did not begin this way at man’s creation and it will not end this way at man’s glorification. Besides, it is an ethical dualism, not cosmological or anthropological.
Before describing the fruit produced by the flesh (vv. 19–21) and those by the Spirit (vv. 22–23), Paul sums up in verse 18 what he has been teaching. He does so in the context of the subversive efforts of the Judaizers to move believers away from the life in the Spirit to bondage to legalism.
They had begun to live the Christian life by faith through the Spirit (3:1–5) and had been “running well” (5:7). They had then become side tracked, however, into living by a set of legalistic standards. All they had to do was return to the Spirit-led life and he would remove the yoke of the law the Judaizers had placed upon their necks (v. 18).
Matthew Henry has the apostle Paul saying that
If, in the prevailing bent and tenour of your life, you be led of the Spirit—if you act under the guidance and government of the Holy Spirit and of that spiritual nature and disposition He has wrought in you—if you make the Word of God your rule and the grace of God your principle—it will hence appear that you are not under the law, not under the condemning, though you are still under the commanding, power of it. . . .
I close this chapter repeating the words of the apostle in 5:13,16,18 in the Amplified New Testament:
For you, brethren, were (indeed) called
To freedom; only (do not let your) freedom be
An incentive to your flesh and an opportunity
Or excuse (for selfishness), but through
Love you should serve one another. . . . But
I say, walk and live habitually in the
(Holy) Spirit—responsive to and
Controlled and guided by the
Spirit; then you will certainly not gratify
The cravings and desires of the flesh—Of human nature without God. . . . But if
You are guided (led) by the (Holy) Spirit
You are not subject to the law.
Murphy, E. F. (1997, c1996). Handbook for spiritual warfare (116). Nashville: Thomas Nelson.