This is very simple. Everyone's vote should be equal. The electoral college ensures that voters are not equal. A farmer living in Idaho doesn't somehow know better what the country needs than a farmer in California.
Republicans are dishonest on this issue. They use every excuse to keep the EC except the one they really believe: It helps republicans win. That's the only reason they favor it. It helps keep dems out of power. That's it.
Every other thing they say about the subject is 100% bullshit.