I'm one of a team of brand specialists at a technology vendor. My teammates represent different vendors, and as a result are effectively my competitors. As a team we are pretty tight knit and we pride ourselves on our close professional relationships built around transparency.

In times past, we uncovered many situations where sales reps were plying us against each other in an effort to see who could jump the highest (not unlike watching two dogs fight over a bone). One way I keep my teammates in the know is to BCC them on a reply to a rep who I suspect of using underhanded tactics to get a sale. It's been fairly successful in keeping things on the level, and we haven't faced any pushback.

Jump to today when I BCC a teammate of mine on an email to a rep who I suspect of being shady. My teammate was sick at home and not reading properly, and responds to the email I had BCC-ed him on. The sales rep goes off on me by saying that looping people in via BCC is "sneaky and lame". I don't think I did anything wrong except maybe not giving him the benefit of the doubt. I told him I how he operates is up to him, and how I do so is up to me and me alone. I continued that if he has an issue, he is more than welcome to take it up with me personally or with my management team. He declined the offer.

AITA for sticking to my guns on this one?