To be fair, a lot of creepy neckbeards on social media are super spergy about loving Kantai Collection. I've seen a handful of Neo-Nazis (there seems to be a rise of these types here anyway) vehemently support it. I also read that it influenced and contributed to a slight rise in nationalism in young Japanese dudes when it came out, similar to "meme magic" garbage in the US. I mean, gotta support your waifus IRL, right?
It's understandable that people don't like it, considering references to the Axis Powers and boats used in World War II to fight for the Nazi regime. I really don't think it has anything to do with being an AMERICAN PATRIOT, it's just that war-based anime tends to be Neo-Nazi magnets and that's off-putting for most people. References to tragedies in World War II usually leave a bad taste in people's mouths.
It's really just similar to the Hetalia situation, or Attack on Titan and imperialist ideology stuff the author puts in. Japan just has a tendency to do this, but knowing their political background, it makes sense. I remember a manga called Afghanis-tan got into a lot of heat about how it portrayed 9/11 (right before the author got caught for hoarding CP). So, I guess it's that. Japan is Japan, so the anime it produces will lean towards its ideals. But in the end, it's just cartoons and people get too serious over it (cough BLmatsu crowd cough).
