To San Diego Tourist Board:
"We regard the decision by San Diego to boycott Arizona as arrogant, ill-willed, and punitive. Naturally, we do not want to be associated with such a decision. Therefore, we are canceling our plans to take a cruise from/to your beautiful city, and will be spending our money enjoying Arizona instead.
Since you yourself are into boycotting, you should understand our thinking, and, I trust, approve of our decision."
PS -- If you really want to consider a principled boycott, you might consider boycotting goods from China, which has a demonstrably worse human rights record than your friends to the east.