> There was literally nothing wrong with the email
There were at least two things wrong with the email, from my perspective as a guy who's been around plenty of benign bro culture.
1. Explicitly mentioning "sex" as opposed to "relationship" or "dating", and talking about it so casually, sets a very aggressive tone. 20-something guys with lots of hormones will definitely hear that tone and push hard for sex during the trip (the implication is that there will be lots of it, and nobody wants to be left out). Females reading this surely know that they'll receive lots of attention and advances during the trip, whether they want it or not – even if you assume that the guys will be asking for consent, it's still uncomfortable for those who want to be professional and avoid work relationships.
2. "Yes, that means that Travis will be celibate on this trip. #CEOLife #FML." Implication there is that there are many people on the team that the Travis wants to sleep with. If you're a female subordinate of the CEO whom he speaks with somewhat flirtily, you can infer that he's thinking "FML, I wish I could sleep with her".