I think the e-mail was in response to the NBA's refusing to allow the Blazers to sign Miles off of waivers. The Blazers believe this was discriminatory behavior by the league that harmed their salary cap situation and costs them money. The league said that any other team could sign him, and use him extremely sparingly to their competitive and financial advantage, but the Blazers couldn't sign him and use him to their competitive and financial advantage. That's not symmetrical, it's not a level playing field, and that's what I think the letter is meant to address.
They sent the e-mail to lay the legal case for an appeal against the league, or at least leverage to get some cap relief. The letter contains language like "violate its fiduciary duty as an NBA joint venturer" and "individually liable to the Portland Trail Blazers for tortuously interfering with the Portland Trail Blazers' contract rights and perspective economic opportunities." I don't think it's aimed at an individual team, it's aimed at the league office for its discriminatory behavior.