Kingreaper
Adventurer
I do, in fact, see it as ridiculous. But the reason it's ridiculous is that I'm forcing the cleric to jump through a lot of silly hoops to justify imposing a penalty on his own attack roll.
To take a less extreme example, suppose the cleric decides to run someplace while ordering the spiritual weapon to attack. I point out that running imposes a -5 penalty on the attack roll. The cleric's player shrugs. "I don't care if I hit, I just want to provide flanking for Stabby McRogue while I get to a safe spot."
At this point, I can try to divine whether the cleric's player is acting primarily out of a desire to acquire a penalty or primarily out of a desire to get somewhere, and allow CA or not based on this guess (which is a recipe for discord at the table).
Or you can go "Alright, well, make the attack first, that way you won't have to take the attack penalty"* and if they go "But I want to miss" you have your answer.
*(because that's how the rules for running work)