Starbucks is responding as some of its union workers took to picket lines Friday after Starbucks Workers United (SBWU) baristas voted to authorize a strike earlier this week.According to the coffee chain, the union is seeking pay hikes that are “not sustainable.”“Workers United proposals call for an immediate increase in the minimum wage of hourly partners by 64% and by 77% over the life of a three-year contract,” Starbucks said in a statement. “This is not sustainable.”According to Starbucks, the average p ...