Earlier quoted context omitted.
I think the point is that no matter how kind you are to those people they'll find a reason to take offense anyway.
In which case there's no reason to be unkind, either! If you can communicate the truth with kindness and be heard, great. If not, move on. In my experience, unkindness isn't any more effective than kindness in effecting change; it usually prompts defensiveness.
One of the human types may be called “emotional extremist”. They push borders until someone explodes in their face, and this is the feedback they use. Not reality or arguments. Cold controlled unkindness that presses them against the wall is much better in this case because otherwise someone will be driven crazy by them.