Making combat optional for certain groups

I was reading this book recently and came upon what I considered a very odd claim. It states that when the American Air Force carried out a bombing raid on Rome, Catholic soldiers were given the option of turning down the mission (but states none did). First of all, is this claim correct? It seems odd the military would make a mission optional. Secondly, do any armies now and then allow specific groups (ethnicities, religions, etc.) to opt out of combat missions? I’m not talking about not being allowed in combat situations, as women were until recently. I’m talking about normally serving in a combat unit but allowing opt outs for certain missions.

Sounds like there was a chance of purposely or accidentally bombing the Vatican or other religious landmarks.

I remember reading some non-fiction book written in the 1980s about potential future wars and went in detail about hypothetical deployment strategies. The only thing I still remember about it was a chapter on a potential invasion of apartheid South Africa by Communist countries bordering it, and in that scenario the US would definitely send forces there to defend it. Notably it made a statement how it was very likely the US military would allow black service members to opt out of taking part in the deployment to prevent them from having the moral dilemma of fighting to keep black Africans disenfranchised.

The French Foreign Legion has a policy of not sending soldiers to fight against their own countrymen (unless they volunteer to do so). For instance in the late 19th, early 20th century, a fairly large number of soldiers in the Foreign Legion were Germans. When units of the Foreign Legion fought in Europe against Germany (during the Franco-Prussian war, WWI and WWII), most German legionnaires stayed in North Africa and Indochina.

Seems like a recipe for discohesion in the unit upon the white troops’ return.

I used to know a black American veteran who would have been on the other side, had that war happened. As of 1989, he expected it to, in some fashion, and was ready to go.