No temples are entirely sacrosanct except those that have built in auras of peace which actively stop attacks from occuring. That said, any time you step into a temple with aggression in mind, you are provoking the god who dwells there, and you may end up a statue, frog, or puff of smoke. That's your choice.
I would say from personal experience that some gods are more strict with this than others. Some will immediately get on your for attacking one of their followers within their temple. Some will chastise you, some will request that you not do it again, and (this has actually happened to me) some will congratulate you on a good kill.
It is impossible to guess how most of the gods will respond to this sort of disrespect. You take your life and your belongings and gamble with them by partaking in such activities, but such is your right.
That said, I've never seen a god punish someone for attacking a non follower in their temple, barring that person being allowed in with someone of the order for a talk, or being there to talk with the god in person.
After all, we've already got the pool for a protected location. If you must have perfect safety, there is your option. It's too bad that so many take complete advantage of the many stockrooms open for abuse, but I see no reason to open up 60 more saferooms where some will go to pray (correctly) and most others will go to sit and have talks with their friends while safe from harm (which is the sort of silliness that hurts these lands).
Battlemage Fistandantilus
Written by my hand on the 27th of Midwinter, in the year 1164.