Here my friend is where I disagree.One other point. Setting someone to dislike is a completly OOC action. So I disagree with the idea that you should react to it at all, such as if you are talking face to face with someone and they set you to dislike, you should not assume that means that character is getting agressive or looking hostile to you.
I think it would be metagaming if you logged in and set me to dislike and I immediatly started buffing because I expected an attack. Thats taking the OOC notion of being set to hostile and applying it ICly.
However if you were arguing with me and we clearly were geting angry with each other and you set me to hostile I would conclude that you took a much more agressive stance towards me ICly.
Perhaps your character started tightening straps on their armor, grabbed their sword and pulled it half way out of the scabbard, started chating/praying softly, reached in your pocket and started mixing spell components, squared your shoulders off towards me or even jusy (though importantly) the tone of your voice and your characters bearing.
In that situation I would see setting someone to hostile as an IC action with IC consiquences.
Not setting someone to hostile across a server. In that case I would assume that if and when I DID meet someone they would immediately be hostile towards me and look like their ready to jump me.