なぜ韓国人は、嫌われるのか？

Almost ALL Japanese assumes Koreans hate Japanese.

Let me make this clear. We, Koreans, don't hate Japanese people. We DO hate past Japanese Imperial government and a few Japanese politicians who make ignorant comments.

Koreans (well, there are always an exception like in any other country) are very well aware that it's extremely dangerous to assume one's personality or integrity based on his/her nationality or race.

For example, Japanese rock group, X-Japan, has tremendous number of followers in Korea. And so as Hidetoshi Nakata, Shiono Nanami, etc.
Would these be possible if Koreans hate Japanese no matter what?

I sense Japanese DO discriminate people. Let me rephrase that. SOME Japanese people discriminate. Well, they decide on people on their national origin.

Japanese say Koreans have no etiquette or manners. Have they seen arabs, iranians, chinese, mexicans, africans, etc.? They say Koreans are barbaric because they eat dogs and chrisalys. Yet, they don't know certain tribes in Alps eating dogs AND cats and Iranians eating uncooked chrisalys. When I visited a Mexican friend of mine, I was introduced to a dog taco.

Things that you call an 'etiquette' or 'manner' is largely defined by one's culture in specific date and time. You can say a culture is moral or immoral or even right or wrong to some extent but you can NOT say that to a person of that culture.
It's not his/her fault to be born in Korea!

All of my Korean friends go crazy if there's a soccer match between Korea and Japan. They would even use the word, "Chok Ba Ri." Yet, they have their own Japanese friends and they really care about them. They believe those Japanese friends of them are true friends as much as their Korean friends because they see their friends as humans not Japanese or Koreans. They all know Japanese people in average are much nicer than average Koreans. They all know current Japanese people have nothing to do with Japan's past. They appreciate Japanese culture such as art, music, consumer products, food, etc. They all want to visit Japan, the home of Dragonball and Slamdunk. They all want to make Japanese friends.

Now, let's go back to the soccer stadium where Korea vs Japan is being held. Those exact same people would shout "Crush Japan!", "anti-Japan all the way!", etc.

Do you get the picture what kind of feelings Koreans have towards Japan and Japanese?

I hope you do.