[It's weird being in a universe where you have to explain 'What's a Decepticon'.]

...One of our factions.

'Cons tend to be fans of the idea of subjugating non-Cybertronians and act like your kind are beneath them. You'll probably get the hint real fast which ones decide to stick with the title.

[He gestures to his chest.]

Their badges are usually purple and triangular - in case the latter wasn't enough to differentiate them.