Sometimes being ultra direct is required.
Too many of us are wearing the burden of stress for other people's lack of awareness.
Being direct is a perfectly acceptable way to remove unnecessary stress from your life.
It's not rude.
It's not impolite.
And it certainly isn’t something that requires an apology.
The truth you give them...as long as it's the actual truth...will give the other party a new sense of awareness that will ultimately help them.
So stop bearing the burden of other's lack of understanding boundaries, and free yourself by telling the truth.