You would use the term when you think it would be in the be in the best interest of the party/s or person/s confronting you to leave and/or leave you alone. It should be stated with feeling.

back away from a confrontation.

Church for gangsters.

Basically, "step off" is a form of brush-off, and/or an order to another individual to get out of your sight. You don't want them talking to you, or even near you. You want nothing to do with them.

Step off is the word you use if you don’t want someone messing with you. Should be said aggressively or with authority like you mean it.

A term used to tell some to leave Right away.

One of the 3 magic words, "please," "thank you," and "step off Bitch."
Used to tell somebody to chill or to step down