What gets the Apostle Paul mad? He had different groups of critics that both said nasty things about him and slandered his ministry. But he reacts differently to them. Why does he fly off the handle when he writes to the Galatians? Why does he shrug off his opponents referenced in Philippians? The difference is the message.
To the Philippians he references some critics of his that are grieving him. They are preaching out of rivalry and are seeking to afflict Paul. But he’s relatively cool about it. Basically he says: no problem, I rejoice because at least they’re proclaiming the Gospel.
But to the Galatians he references another group of critics. But this time he says they ought to be accursed. Why? Because the difference is not personal, it is about the heart of the Gospel.
The “Galatian” opponents were saying that to be saved:
1) First a man believes in Christ, 2) then he keeps God’s law as best he can, 3) and then he is justified (made right before God)
The “Philippian” opponents were saying that to be saved:
1) First a man believes in Christ, 2) then he is justified, 3) then he proceeds to keep God’s law
Do you see the difference? Do you see why in one case he shrugs and the other he blows his top? Do you see why it is so important to get this part of the Gospel right?
* This is paraphrased from J Gresham Machen’s classic Christianity & Liberalism, pages 19-21. Not a single observation is my own.