Um.... not to reveal too much about myself irl but... I work for SBux and talk about the Co$ as a cult with my co-workers and occassionally customers all the time and I have heard
nothing about this...
SBux is non-partisan as a company. They won't refuse service to anyone. Especially not to a group of nameless individuals. If I were to hazard a guess... I would say that this is a rumor started by Co$ to scare Anons with the implication that they have big name companies supporting them.
Edit: I reread my post and it doesn't say what I want it to: SBux is unlikely to say anything about it above and beyond declaring that they are non-partisan and will not refuse service to anyone.
Edit #2: All press releases from SBux are posted on their website:
Press Release Archive