Paul of Tarsus cursed all Trinitarians in Galatians 1 as Paul of Tarsus never knew about the Trinity doctrine and never preached or believed in this doctrine. Thus for Paul of Tarsus, the Trinitarians preach a different Gospel to him, meaning they are cursed according to Galatians 1:8
But even if we or an angel from heaven should preach to you a gospel contrary to the one we preached to you, let him be accursed.
For the Muslim, Paul of Tarsus has no authority whatsoever. Muslims don’t care who he cursed. Can Christians say the same?