First of all, Why would you even do this in America? And Second no its not because it disrespects them and you possibly could get arrested for it.
You are so sternly.
Look at them very, VERY sternly
Admonish is a verb that means to sternly reprimand someone. It can also mean to give someone a warning or advice.
I can give you several sentences.He spoke sternly to the misbehaving students.I backed down when he glared sternly at me."Follow your orders," the sergeant said sternly.
If it's a meaning you want, 'sternly' means 'harshly' or 'firmly'.
Example sentence - His father spoke sternly to him when he behaved badly.
Reprimanded
Firm or unyielding, uncompromising.
Lamented or sternly
They are synonyms, not antonyms.
Meaning hard, harsh, or severe in manner or character:
it means with sternness; in a severe manner.