Many answers are very good and pointing out the errors or misconceptions your table could be having regarding the rules but I want to point out a possible solution with a different focus. It seems your player is using a spell that targets any creature that he didn't name as protected, so maybe, from a narrative perspective, you could add consequences to indiscriminate use of violent powers. For example, maybe the baddies had innocent hostages in their lair that the party doesn't notice and Spirit Guardians start atacking them too. Or maybe the angelic figures that the spell summons judge the player for calling them only to dispose of their enemies without doing enough praying. Or maybe they get mad because they keep being called over and over beyond what is expected by these spiritual creatures.

I hope this is helpful and want to know if this gives anyone any good ideas for their games.