In answer to your question, what happened is that a large group of Open Carry advocates in the SF Bay area met at Peet's Coffee and Tea. The antis found out and convinced Peet's to ban guns from the premises. So our brethren went to California Pizza Kitchen with the same results.
Finally, the group made it to Starbucks, who responded to the Brady Campaign's request to ban guns by issuing a statement that said "We will follow state law on this issue." The Brady's didn't like that, so they've been crying and moaning and protesting ever since.
What it comes down to is that Starbucks didn't back down.
Now, sit down, shut up, and let me buy you a latte.