expostulation

[L. expostulatio.]
The act of expostulating or reasoning with a person in opposition to some impropriety of conduct; remonstrance; earnest and kindly protest; dissuasion.

We must use expostulation kindly.

noun

The act of expressing strong or reasoned opposition: challenge, demur, exception, objection, protest, protestation, remonstrance, remonstration, squawk. Slang kick. See support/oppose.

The noun has 2 meanings:

Meaning #1: the act of expressing earnest opposition or protest
  Synonyms: remonstrance, objection

Meaning #2: an exclamation of protest or remonstrance or reproof