It’s one of those things that has a mental affect on you out of all proportion to the physical. As you see his spit gathering into a blob that you know will fall directly into your mouth, that you know you will be expected to swallow, you cringe mentally.
Why? If he were to kiss you you’d be swallowing that much of his saliva and you’d be welcoming it!
But this slow deliberate spitting in your mouth isn’t anything like a kiss. A kiss is between equals - this is between a Superior Being and something lesser, something infinitely inferior.
And when you swallow His spittle you weep, knowing that you have just accepted that you are now owned and controlled, and accept that He can do whatever He wants with you.