I can further go into this discussion but I'm tired, I work midnight shift and as such I'm going to bed.... but a quick point.
What might be harmless to us could be deadly for them. Maybe they certain colors can put them into comas, maybe they are affected by certain radiations or radio signals, maybe they fought other species that were no anymore advanced then cave dwellers that are armed with sticks and stones.
They are movies. Battle: Los Angeles is an american war movie about patriotism, comradeship, sacrifice, and service before self. The use of aliens is politically correct, they are a no name bad guy.
Last time I check the remake of Red Dawn pissed off the Communist Government in China. The bad guys in the remake were PRC troops invading the Washington State Coast with Russian support. The original film had the Soviet Union invading the USA with South American support. But the PRC complained and MGM made them happy and went into the movie and replaced all references to the PRC with North Korea. Same thing happened with the video game "Home Front". It originally was a PRC invasion except the PRC complained and that was changed to North Korea.