what would happen from the apostate's point of view if the spell were cast on him/her?
And in the fiction, what would the target experience if a cleric for whom he/she had no personal respect cast the spell?
I think, by the rules, the character would be mind-controlled. It's never been clear exactly what, in D&D, that feels like - maybe the character feels elation in the divine presence while the spell is in effect, and then - when it wears off - returns to feeling disdain towards the cleric and/or the cleric's god.
I get that you feel this is an important thing to have in a game. But do you really see no difference in how the various "vocations" affect the expected dynamics of the party? Being a fierce warrior, singing the music of creation, or making a pact with a devil don't bring with them implications about how the other PCs will relate to them.
This is the bit where we don't agree.
Making a pact with a devil brings with it an implication that my PC won't complain about your PC having made a pact with a devil.
Being a cleric brings with it an implication that my PC won't complain about you mind-controlling me by casting Bless.
You being a battle-master who uses ally-boosting manoeuvres brings with it an implication that I won't feel it cheapens my sense of my PC's talent that you can help improve my action economy.
And building a fighter, no matter how pious, brings with it an implication that the gods will generally decline to hear my prayers - even if I'm locked in mortal combat with an evil cultist.
I think that, in a lot of D&D play, these points of detail are just ignored. The table simply doesn't drill this far down into the fiction.
At tables where there
is this sort of drilling down into the fiction, I don't see that the warlord is in a particularly different boat. The table has to find some way of reconciling the details of party play, and PC builds, and class-siloisation, with their prepared conception of the fiction.