I'm speaking in the context of tact. When someone is being tactless, they are communicating to achieve a goal without regard for the social implications of said communication.
The tactlessness has no relationship with the underlying honesty of the goal, though it makes the communication itself less honest.
> As someone who has said some really hurtful things, I can’t tell you how much it pains me to have my thoughtlessness mistaken for cruelty.
If it was throughtless or innacure, dont call it honesty then. It is not honesty no matter how brutal.
And yes, people do say hurtful untrue things on purpose. Or they just say them, but then they insist on them knowing it was throughtless.