(edit: sent mid sentence on accident)

Every interaction between humans is manipulation. Every single one - including not saying something.

With that framing: Your question sounds to me about the negative connotation ("being manipulative") - and for me that's simple: sincerity and intent.

Before coming to your last paragraph I go with an extreme as example, abuse, because it's so black and white:

I try to convince you to leave your abusive partner. I try to alter your whole life - because I'm convinced that it's the right thing for you.

If I tell you the same thing to get off with your current partner or to harm you, it's manipulative.

Now for your example: For me it's the foundation of our human interaction to bridge gaps - social, communicative, personal.

We always have incomplete data sets (if only about the perception, interpretation and knowledge of the other people around us). We're always in an interpretation gap.

Now if you withhold information other humans are worse off, even ignoring what other people call "the objective truth": they don't know where you stand, what your reasoning is and what values you hold. All of this shines through even when just saying, as a random example, "I don't want bacon" - this can be health, religion, mood, taste and a miryad of other things related that will help other people connect (or avoid) you.

In short: don't break other people's heads! Every human needs to evaluate information they get - as long as you're sincere and don't try to evoke a behavior that you know is against the best of your surrounding you wouldn't fall into "manipulative" in my book.