Exactly this. Even though we were engaging in regular competition, us simply mentioning that we wanted to "kill them" or "wipe them out" could be falsely construed as us trying to use illegal means to do so, which we weren't.

And that's the point. Lawyers can twist things written in emails to be whatever they want. People who say "if you're not doing anything illegal, then you have nothing to hide" has never been at the hands of a witch hunt. I have a friend who lived in the US on F1 and H1B for over 10 years and was banned from entering the US over jokes with her ex-bf about marrying for a green card.