The title of this thread is completely misleading. In fact, it is a total lie (and we should all know who the "father of lies" is.
Starbucks workers HAVE NOT voted to unionize. Starbucks workers at three different Buffalo, NY locations (and only these three) have won the right to have a vote on whether to unionize or not. The vote will not affect workers at any other Starbucks in the United States, though if the Buffalo, NY vote is successful it perhaps might encourage staff at other Starbucks locations to petition to have a vote to unionize. Only 100 employees will be voting and the vote doesn't take place until December 8.
An $8.00 (7%) drop from a stock value of $114.43 is hardly a tumble. Sometimes this can be a good situation for the company, though not investors ... the higher the stock value the more dividends the company has to pay.
Any way's I live in the home turf of Starbucks (Washington State) and regardless of how many locations may or may not vote to unionize, I do not expect they to go out of business anytime soon, or ever.