The Greeks hate it? Where'd you hear this?
It was a apparently a group of socialists who are afraid this will incite nationalist pride.
There is a concerted effort (across all of europe) to demonize nationalist pride. IOW their PC crowd wants to forbid pride for being Greek (or italian, or french, or spanish, or german, or british) but to only only think of themselves as european.
Keep in mind if these politicians (like the democrats of the USA) were in charge of the spartans, they would have surrendered first and thought later.
The REST of the greek population is very pleased with the movie. (blood fest and all)