The big difference is what we are saying is true.... in the second case:
"I have an emotional reaction X" We're saying that it is true that you are having this experience. But if you said "Murder is yucky" then there is no way to determine whether or not this statement is true, because it is a value judgment about murder. Its not about whether or not you find it yucky or not.
Another way of thinking about this:
"Murder is yucky" is a subjective statement that requires the use of a value to analyze the truth or falsity of.
"I am having an emotional reaction to murder that is unpleasant" is an objective statement that hinges on whether or not it is true in reality that the person this sentence references is indeed in this particular emotional state because of the idea "murder."