It wasn't a tax on the colonists that caused them to protest. The Tea Act of 1773, removed the export duty on tea only for the East India Company, and this is what the colonists were protesting because this exemption meant that they couldn't compete with the East India Company, and it was also a protest against the power that large crown corporations had in influencing the decisions made in parliament.

It was not a protest against a tax. It was a protest against a corporate tax break.