Calvinists do not like the concept of natural law, because with it, Total depravity must be error. If total Depravity is error, all of Calvinism must fall with the exception of the 'P'.
I went ahead and posted the rest of it. If the Law condemns the Jews, and the Gentiles do by nature the things contained in the Law, then the Gentiles, in trying to live up those things, are also condemned. That's the point Paul is trying to make here. Jew or Gentile, Law or natural understanding, ALL are guilty, ALL have sinned, and ALL will be judged accordingly. Why are you trying to turn this into some sort of justification for man? The Law condemns him, Jew or Gentile! That which is written on their hearts is enough to damn them all to Hell! Rather than undermining Total Depravity, this passage affirms it!