I found it; finally after all these years, I think I can put a Biblical word to it. Vague accusation would be called "murmuring." I'm writing this in general, not to any one person, because I've experienced this countless times, especially over email.
The confusion is that murmuring is typically considered people speaking under their breath, in a low voice, or what I would call a cowardly manner, not coming forth to speak clearly and openly. However, it has another meaning in Scripture that I found in my research today.
murmur (n): a complaint half suppressed, or uttered in a low, muttering voice
In the instance of a verbal murmur, it's done in a low voice; however, in writing, that tone cannot be expressed, and it ends up being a complaint half-suppressed, meaning that it's a sideways attempt at bringing forth a complaint, rather than being straightforward.
How long shall I bear with this evil congregation, which murmur against me? I have heard the murmurings of the children of Israel, which they murmur against me.
-Num 14:27
The Jews then murmured at him, because he said, I am the bread which came down from heaven. And they said, Is not this Jesus, the son of Joseph, whose father and mother we know? how is it then that he saith, I came down from heaven? Jesus therefore answered and said unto them, Murmur not among yourselves.
-John 6:41-43
In this instance, they were uttering complaints under their breath, instead of coming straight out and accusing him directly. However, the general concept of murmuring is not speaking openly and straightforward.
And there was much murmuring among the people concerning him: for some said, He is a good man: others said, Nay; but he deceiveth the people. Howbeit no man spake openly of him for fear of the Jews.
-John 7:12-13
The Lord God wants us to be open, honest, and straightforward, not to mutter under our breath, or present accusations that are disguised as questions, or present complaints that wear the costume of a compliment. I am often, VERY often, criticized for drawing out murmurings, being falsely accused of being prideful because most other people think I'm just "trying to be right," but it is a matter that, when I see sin, or the things that God hates, like murmurings, I will point them out, even if everyone hates me for it, because to do what is right and turn people away from sin to the Living God is pleasing in His sight; it also stops the leaven before it begins, and let's others know that they also need to fear God.
Them that sin rebuke before all, that others also may fear.
-1Ti 5:20
There are many who don't do this because they are afraid; not of God, but of men. They do not put their trust in God that they will be protected from the wicked.
The fear of man bringeth a snare: but whoso putteth his trust in the LORD shall be safe.
-Pro 29:25
So no matter how many people that come on here and want to get angry with me about a matter, I'm going to tell the truth. I try to be kind about telling people the truth when they come to me and want to talk about a matter, but I can say with honesty that I have very little patience for murmuring. Those of you who have been in our church for a long time know that if you come to us with straightforward attitude that's completely honest, we don't berate, badger, or condemn you.
Let's all do our best to be perfect before our Father in Heaven and cut out all murmuring from His church.