I'm open to trading Julien (or any player who seems to lack a long-term, non-utility position) if the return is right. This is not.
I also question why the Twins would want to make Boston better if they're the top competition for the wild card right now.
Broader question: what is worse? Trading in-division or with the teams in wild card contention? I'd definitely say the latter, with an exclusion for the division leader. Zero short-term harm in a trade with bottom dwellers.