To quote the great Nicholas Meyer (Director of Wrath of Khan) who spoke on this topic:
“Roddenberry had his own utopian vision about the perfectibility of man, and I never really believed that. And I don’t think the show demonstrates that. I think it is about gunboat diplomacy. In the final analysis, the Enterprise fires. They’re always shooting and bringing civilization, and coming to worlds where they don’t approve of tyrannical enterprises – no pun intended – and they substitute their own quote unquote enlightened version of how society is supposed to work, which is essentially American.”