All of which is true but completely irrelevant to the your average "tea party" merchant. The reason why he is on that boat is that he can't compete with the government controlled trade in tea where the EIC get a tariff break.
Note that Tea is actually cheaper for the consumer so the "tax" has been reduced. Even with "representation" the colonists could not avoid this scenario unless they challenge the right of national governments to control their tariffs.
That doesn't mean that ending the Mercantile system wasn't a legitimate aim for an independence movement - just that its a little less clear cut to sell to the masses than "no taxation without representation" - particularly because none of the "tea party" merchants wanted free trade (as that would create more competition and lower profits) and some actually smuggled the stuff.
The tea is only cheaper for the consumer if the EIC doesn't start unilaterally putting up prices, which they would inevitably do once the system was in place.
And yes, I get that the Boston Tea Party/Sons of Liberty brigade were demagogues and rabble-rousers. I just think that the state and continental assemblies, who were the rightful centre of protest, were much more rational and had completely legitimate opposition to the Tea Act. People like Ben Franklin condemned the Tea Party, for what it's worth.