Seriously, if 4th of July offends a liberal, wait until they visit Australia and they realise that Australia had a "dark" history such as the White Australia Policy, "Invasion" Day, and the "Stolen Generations".
What actually happened in Australia may seem worse than what Americans went through but why be offended for saying 4th of July!
White Australia Policy: People in Australia had a different culture 100 years ago, white supremacy was legal because it was supposed to protect the economy as technology hasn't evolved that much.
"Invasion" Day: Just a great day for British to take Australia, would have been worse if the French or Spanish colonised Australia because we would have had no Indigenous Australians left.
"Stolen Generations": Just a part of the White Australia Policy which was supposed to protect children of Aboriginal and Torres Strait Islander ancestry from these massacres which were racist, but please, the "stolen generations" weren't really stolen, it was better to do this than lose culture from massacres. God bless these children.