From what I understand, as it would be excessive to forbid a plainly descriptive phrase that reasonably refers to a TSO as the phrase stands on its own, that one's kosher if you don't do anything to draw attention to the acronym it forms.

Example:
Saying "Joe was displeased with the airport security screeners at ORD last week" is okay.

Saying "I can't believe what that Airport Security Screener (note caps and bolding versus in-flow formatting of prior example) did to him!" is not.

And obviously, just spelling out the acronym with periods after each letter is not.

Such is my understanding of the rule.