He was hoping the authoritarian tone would have had some impact, and the organic's insistence on questioning him only increases his irritation. He isn't fond of lying, but keeping cover is far more important. He doesn't realize that they may have come across Cybertronians in the past. There's really nothing he can do in this situation but expand on his bluff and hope it finally makes an impact.

"This is a classified military operation surveying suspicious activity in the area. Once again, please remove yourself from the premises."