In my 4 years as a Captain here, here are the 3 things I've been asked to explain.

Refusing an aircraft to go to Africa. Mx agreed with me. They got ne a new plane and we left an hour late. -this was a CA CP, he was 100% on board with my decision, but I'm not sure if a less than 2 years here on a domestic only fleet ACP who had never been a CA at the regional would have understood my logic.

Requesting an A be replaced because I had concerns she wouldn't listen after she flat out blew me off when I told her we were deplaning due to inability to keep cabin at any reasonable temperature. I had already expanded team and OCC/MCC said it's my call but they'd agree with it if I did.
-this call was from an ACP I knew from a previous job, and he agreed with me.

Refusing to fly OAK-SFO after 2 windshear events at SFO, our alternate closing, and diverting again to OAK and landing with fuel low enough that we had to do paperwork. We were pushing the 9:00 hard block limit and they had us planned 20 minutes gate to gate. No way. We were fried.
-ACP with very limited experience, questioned why we couldn't "just take the extension" and I had to explain there was no extension on the block limit and even if there was I didn't feel safe to continue.

So 2 out of 3 were no problem just wanted to know what the deal was but one was having to explain myself to someone who hadn't been in the position.