Smerel, are you engaging in “the ends justifies the means”?
He was able to save jews; even if that was due to his entering churches, and if he didn’t he wouldn’t be in that position(unlikely, because fulfilling the Torah raises our esteem among the nations) Hashem would have found a different shliach.
Chazal allowed emissaries to do many things. I don’t know why referring to entering a church is being reduced to “they allowed stam yainom, kal vechomer churches” – who told you entering a church is a small thing? Stam yainom is derabonon. I’m not sure what particular issur entering a church is, but i believe it’s abuzrayhu AZ, which is deoraysoh.
Re, protestants/Catholics. The only issue that’s “less” AZ is the lack of statues. The theology is more or less the same; they both believe in the trinity, pray to yushke(Catholics allow praying to mary, protestants don’t) and believe in yushke as godly r”l. That makes their worship 100% AZ for jews, and shituf for goyim, which according to a minority opinion might not be in the 7 mitzvos.
That’s if a religious service is being held in the church, including any prayer service. Even the British national anthem includes an element of prayer, as it says “g-d save the queen/king” – who, in a church, are they referring to when they ask their god to save the queen/king? That’s a serious issue