most South koreans do not eat dogs. very few people of the current generation have ever eaten it, and even the people that have (of any generation) do not eat it often.
that said, the dogs that are eaten are bred for that purpose. you aren't playing with fido one day and then chopping him up for dinner the next
consumption of dog stems from a time when korea as a whole was very poor (which is very recent in the grand scheme of things--my father in law remembers not having three meals a day, and when the Americans came to help with the Korean war, the Korean soldiers were totally weirded out by milk cartons bcuz they were paper holding liquid but not getting soaked, etc.). that is not korea today