In a free society, people have the right to decide what to purchase (within loose limits) and what not, for whatever reasons they may have. You make a poor attempt at deligimising their genuine exercise of this right by slandering them with the 'transphobe' label. That is reductive, oversimplistic, and demonstrates poor understanding of fundamental realities.

Disagreement with mainstream Western gender narratives is not phobia. Deciding against enriching a propagator of an idea you disagree with is not phobia either. These are rational, decent, civilized forms of voting with one's wallet. You do it yourself when you choose environmentally sensitive brands or boycott Harvey Weinstein.

I would be more ready to accept the 'phobia' label if, say, there were violent riots and arson on Starbucks property, or calls to ban the buisness.