"Behold, I will make them of the synagogue of Satan, which say they are Jews, and are not, but do lie; behold, I will make them to come and worship before thy feet, and to know that I have loved thee."
-Revelation 3:9

who are the "synagogue of Satan"?.............are they the Judaizers of Galatians?

You are told by Jesus not to point your finger at anybody, not because you have 3 pointing back at you, but because who you are pointing at could more righteous than you.

The Judaizers were just following their interpretations of the law and they weren't wrong. What they were wrong about was to be a follower of Christ you had to practice the strict laws of the people who were devout Jews. That would make them more right to follow the laws than you were to follow their laws. Christ does not deny them. The people of Galatia had synagogues and they were run by devout Jews who practised things like circumcision, not eating pork, etc. Peter, James, and John practised those things, but Paul, Barnabbas, and Titus did not. Titus wasn't even an apostle. But he wasn't a synagogue of Satan, either.
The 'synagogues of Satan' are those people that believe that Jesus Christ is not the saviour of mankind.

They are tares,,,,,they are those that were planted at the beginning of the age,,,,the same ones that invaded the preisthood.....They are those who screamed "CRUCICY HIM CRUCIFY HIM.....they are known as the sons of Cain....